Method for purifying contaminated polymers

ABSTRACT

A method for purifying a reclaimed polymer, such as a polymer reclaimed from post-consumer use or post-industrial use, is disclosed. The method involves obtaining the reclaimed polymer and contacting it at an elevated temperature and pressure with a fluid solvent to produce an extracted reclaimed polymer. The extracted reclaimed polymer is dissolved in a solvent at an elevated temperature and pressure to produce a polymer solution, which is purified at an elevated temperature and pressure by contacting the polymer solution with solid media to produce a purer polymer solution. A purer polymer is then separated from the purer polymer solution.

FIELD OF THE INVENTION

The present invention generally relates to a method for purifyingcontaminated polymers through the use of a pressurized solvent and solidmedia. More specifically, this invention relates to a method forpurifying recycled polymers, such as post-consumer and post-industrialrecycled plastics, to produce a colorless or clear, odor free,virgin-like polymer. It is particularly useful for the purification ofpolyolefins, such polyethylene and polypropylene.

BACKGROUND OF THE INVENTION

Polymers, especially synthetic plastics, are ubiquitous in daily lifedue to their relatively low production costs and good balance ofmaterial properties. Synthetic plastics are used in a wide variety ofapplications, such as packaging, automotive components, medical devices,and consumer goods. To meet the high demand of these applications, tensof billions of pounds of synthetic plastics are produced globally on anannual basis. The overwhelming majority of synthetic plastics areproduced from increasingly scarce fossil sources, such as petroleum andnatural gas. Additionally, the manufacturing of synthetic plastics fromfossil sources produces CO₂ as a by-product.

The ubiquitous use of synthetic plastics has consequently resulted inmillions of tons of plastic waste being generated every year. While themajority of plastic waste is landfilled via municipal solid wasteprograms, a significant portion of plastic waste is found in theenvironment as litter, which is unsightly and potentially harmful toecosystems. Plastic waste is often washed into river systems andultimately out to sea.

Plastics recycling has emerged as one solution to mitigate the issuesassociated with the wide-spread usage of plastics. Recovering andre-using plastics diverts waste from landfills and reduces the demandfor virgin plastics made from fossil-based resources, which consequentlyreduces greenhouse gas emissions. In developed regions, such as theUnited States and the European Union, rates of plastics recycling areincreasing due to greater awareness by consumers, businesses, andindustrial manufacturing operations. The majority of recycled materials,including plastics, are mixed into a single stream which is collectedand processed by a material recovery facility (MRF). At the MRF,materials are sorted, washed, and packaged for resale. Plastics can besorted into individual materials, such as high-density polyethylene(HDPE) or poly(ethylene terephthalate) (PET), or mixed streams of othercommon plastics, such as polypropylene (PP), low-density polyethylene(LDPE), poly(vinyl chloride) (PVC), polystyrene (PS), polycarbonate(PC), and polyamides (PA). The single or mixed streams can then befurther sorted, washed, and reprocessed into a pellet that is suitablefor re-use in plastics processing, for example blow and injectionmolding.

Though recycled plastics are sorted into predominately uniform streamsand are washed with aqueous and/or caustic solutions, the finalreprocessed pellet often remains highly contaminated with unwanted wasteimpurities, such as spoiled food residue and residual perfumecomponents. In addition, recycled plastic pellets, except for those fromrecycled beverage containers, are darkly colored due to the mixture ofdyes and pigments commonly used to colorize plastic articles. Whilethere are some applications that are insensitive to color andcontamination (for example black plastic paint containers and concealedautomotive components), the majority of applications require non-coloredpellets. The need for high quality, “virgin-like” recycled resin isespecially important for food and drug contact applications, such asfood packaging. In addition to being contaminated with impurities andmixed colorants, many recycled resin products are often heterogeneous inchemical composition and may contain a significant amount of polymericcontamination, such as polyethylene (PE) contamination in recycled PPand vice versa.

Mechanical recycling, also known as secondary recycling, is the processof converting recycled plastic waste into a re-usable form forsubsequent manufacturing. A more detailed review of mechanical recyclingand other plastics recovery processes are described in S. M. Al-Salem,P. Lettieri, J. Baeyens, “Recycling and recovery routes of plastic solidwaste (PSW): A review”, Waste Management, Volume 29, Issue 10, October2009, Pages 2625-2643, ISSN 0956-053X. While advances in mechanicalrecycling technology have improved the quality of recycled polymers tosome degree, there are fundamental limitations of mechanicaldecontamination approaches, such as the physical entrapment of pigmentswithin a polymer matrix. Thus, even with the improvements in mechanicalrecycling technology, the dark color and high levels of chemicalcontamination in currently available recycled plastic waste preventsbroader usage of recycled resins by the plastics industry.

To overcome the fundamental limitations of mechanical recycling, therehave been many methods developed to purify contaminated polymers viachemical approaches, or chemical recycling. Most of these methods usesolvents to decontaminate and purify polymers. The use of solventsenables the extraction of impurities and the dissolution of polymers,which further enables alternative separation technologies.

For example, U.S. Pat. No. 7,935,736 describes a method for recyclingpolyester from polyester-containing waste using a solvent to dissolvethe polyester prior to cleaning. The '736 patent also describes the needto use a precipitant to recover the polyester from the solvent.

In another example, U.S. Pat. No. 6,555,588 describes a method toproduce a polypropylene blend from a plastic mixture comprised of otherpolymers. The '588 patent describes the extraction of contaminants froma polymer at a temperature below the dissolution temperature of thepolymer in the selected solvent, such as hexane, for a specifiedresidence period. The '588 patent further describes increasing thetemperature of the solvent (or a second solvent) to dissolve the polymerprior to filtration. The '588 patent yet further describes the use ofshearing or flow to precipitate polypropylene from solution. Thepolypropylene blend described in the '588 patent contained polyethylenecontamination up to 5.6 wt %.

In another example, European Patent Application No. 849,312 (translatedfrom German to English) describes a process to obtain purifiedpolyolefins from a polyolefin-containing plastic mixture or apolyolefin-containing waste. The '312 patent application describes theextraction of polyolefin mixtures or wastes with a hydrocarbon fractionof gasoline or diesel fuel with a boiling point above 90° C. attemperatures between 90° C. and the boiling point of the hydrocarbonsolvent. The '312 patent application further describes contacting a hotpolyolefin solution with bleaching clay and/or activated carbon toremove foreign components from the solution. The '312 patent yet furtherdescribes cooling the solution to temperatures below 70° C. tocrystallize the polyolefin and then removing adhering solvent by heatingthe polyolefin above the melting point of the polyolefin, or evaporatingthe adhering solvent in a vacuum or passing a gas stream through thepolyolefin precipitate, and/or extraction of the solvent with an alcoholor ketone that boils below the melting point of the polyolefin.

In another example, U.S. Pat. No. 5,198,471 describes a method forseparating polymers from a physically commingled solid mixture (forexample waste plastics) containing a plurality of polymers using asolvent at a first lower temperature to form a first single phasesolution and a remaining solid component. The '471 patent furtherdescribes heating the solvent to higher temperatures to dissolveadditional polymers that were not solubilized at the first lowertemperature. The '471 patent describes filtration of undissolvedcomponents.

In another example, U.S. Pat. No. 5,233,021 describes a method ofextracting pure polymeric components from a multi-component structure(for example waste carpeting) by dissolving each component at anappropriate temperature and pressure in a supercritical fluid and thenvarying the temperature and/or pressure to extract particular componentsin sequence. However, similar to the '471 patent, the '021 patent onlydescribes filtration of the precipitated component.

In another example, U.S. Pat. No. 5,739,270 describes a method andapparatus for continuously separating a polymer component of a plasticfrom contaminants and other components of the plastic using a co-solventand a working fluid. The co-solvent at least partially dissolves thepolymer and the second fluid (that is in a liquid, critical, orsupercritical state) solubilizes components from the polymer andprecipitates some of the dissolved polymer from the co-solvent. The '270patent further describes the step of filtering thethermoplastic-co-solvent (with or without the working fluid) to removeparticulate contaminants, such as glass particles.

The known solvent-based methods to purify contaminated polymers, asdescribed above, do not produce “virgin-like” polymer. In the previousmethods, co-dissolution and thus cross contamination of other polymersoften occurs. If adsorbent is used, a filtration and/or centrifugationstep is often employed to remove the used adsorbent from solution. Inaddition, isolation processes to remove solvent, such as heating, vacuumevaporation, and/or precipitation using a precipitating chemical areused to produce a polymer free of residual solvent.

Accordingly, a need still exists for an improved solvent-based method topurify contaminated polymers that uses a solvent that is readily andeconomically removed from the polymer, is relatively simple in terms ofthe number of unit operations, produces a polymer without a significantamount of polymeric cross contamination, produces a polymer that isessentially colorless, and produces a polymer that is essentiallyodorless.

SUMMARY OF THE INVENTION

A method for purifying a reclaimed polymer is disclosed. The methodcomprises obtaining the reclaimed polymer wherein the reclaimed polymeris selected from the group consisting of post-consumer use polymers,post-industrial use polymers, and combinations thereof. The reclaimedpolymer is contacted at a temperature from about 80° C. to about 220° C.and at a pressure from about 150 psig (1.03 MPa) to about 15,000 psig(103.42 MPa) with a first fluid solvent having a standard boiling pointless than about 70° C., to produce an extracted reclaimed polymer. Theextracted reclaimed polymer is dissolved in a solvent selected from thegroup consisting of the first fluid solvent, a second fluid solvent, andmixtures thereof, at a temperature from about 90° C. to about 220° C.and a pressure from about 350 psig (2.42 MPa) to about 20,000 psig(137.90 MPa) to produce a polymer solution. The polymer solution ispurified at a temperature from about 90° C. to about 220° C. and at apressure from about 350 psig (2.42 MPa) to about 20,000 psig (137.90MPa) by contacting the polymer solution with solid media to produce apurer polymer solution. Then a purer polymer is separated from the purerpolymer solution. In one embodiment, the second fluid solvent has eitherthe same chemical composition or a different chemical composition as thefirst fluid solvent.

In one embodiment, the purer polymer is separated from the purer polymersolution at a temperature from about 0° C. to about 220° C. and apressure from about 0 psig (0 MPa) to 2,000 psig (13.79 MPa).

In one embodiment, the reclaimed polymer is polystyrene. In anotherembodiment, the reclaimed polymer is poly(dimethylsiloxane).

In one embodiment, the reclaimed polymer is post-consumer recyclederived polymer. In another embodiment, the reclaimed polymer is apolypropylene homopolymer or a primarily polypropylene copolymer. Inanother embodiment, the polymer is a polyethylene homopolymer or aprimarily polyethylene copolymer.

In one embodiment, the fluid solvent has a standard boiling point lessthan about 0° C. and greater than about −45° C. and a standard enthalpychange of vaporization of less than about +25 kJ/mol. In anotherembodiment, the fluid solvent is selected from the group consisting ofolefinic hydrocarbons, aliphatic hydrocarbons, and mixtures thereof.

In one embodiment, the aliphatic hydrocarbon is selected from the groupconsisting of C₁-C₆ aliphatic hydrocarbons and mixtures thereof. Inanother embodiment, the aliphatic hydrocarbons and mixtures thereof iscomprised of primarily C₄ aliphatic hydrocarbons.

In one embodiment, the fluid solvent consists essentially of C₄liquefied petroleum gas. In another embodiment, the fluid solvent isn-butane, butane isomers, or mixtures thereof.

In one embodiment, the temperature in the extraction, dissolution, andpurification steps is from about 110° C. to about 170° C.

In one embodiment, the pressure in the contacting step is from about1,100 psig (7.58 MPa) to about 5,500 psig (37.92 MPa).

In one embodiment, the pressure in the contacting step is less thanabout 1,100 psig (7.58 MPa).

In one embodiment, the pressure in the dissolving step is greater thanabout 1,100 psig (7.58 MPa). In another embodiment, the pressure in thedissolving step is greater than about 5,500 psig (37.92 MPa).

In one embodiment, the solid media is selected from the group consistingof inorganic substances, carbon-based substances, and mixtures thereof.In another embodiment, the inorganic substances are selected from thegroup consisting of oxides of silicon, oxides of aluminum, oxides ofiron, aluminum silicates, amorphous volcanic glasses, and mixturesthereof. In another embodiment, the inorganic substances are selectedfrom the group consisting of silica, silica gel, diatomite, sand,quartz, alumina, perlite, fuller's earth, bentonite, and mixturesthereof. In another embodiment, the inorganic substance is reclaimedglass.

In one embodiment, the carbon-based substances are selected from thegroup consisting of anthracite coal, carbon black, coke, activatedcarbon, cellulose, and mixtures thereof. In another embodiment, thecontacting of the polymer solution with the solid media is done in apacked bed of the solid media. In one embodiment, the packed bed isgreater than 20 cm in length.

Additional features of the invention may become apparent to thoseskilled in the art from a review of the following detailed description,taken in conjunction with the examples.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block flow diagram showing the major steps of one embodimentof the present invention.

FIG. 2 is a calibration curve for the calculation of polyethylenecontent in polypropylene using enthalpy values from DSC measurements.

FIG. 3 is a schematic of the experimental apparatus used in the examples

FIG. 4 is a photograph of the polypropylene example specimens.

FIG. 5 is a bar chart of the opacity and odor intensity of severalpolypropylene examples.

FIG. 6 is a photograph of the polyethylene example specimens.

FIG. 7 is a bar chart of the opacity and odor intensity of thepolyethylene examples.

DETAILED DESCRIPTION OF THE INVENTION I. Definitions

As used herein, the term “reclaimed polymer” refers to a polymer usedfor a previous purpose and then recovered for further processing.

As used herein, the term “post-consumer” refers to a source of materialthat originates after the end consumer has used the material in aconsumer good or product.

As used herein, the term “post-consumer recycle” (PCR) refers to amaterial that is produced after the end consumer has used the materialand has disposed of the material in a waste stream.

As used herein, the term “post-industrial” refers to a source of amaterial that originates during the manufacture of a good or product.

As used herein, the term “fluid solvent” refers to a substance that mayexist in the liquid state under specified conditions of temperature andpressure. In some embodiments the fluid solvent may be a predominantlyhomogenous chemical composition of one molecule or isomer, while inother embodiments, the fluid solvent may be a mixture of severaldifferent molecular compositions or isomers. Further, in someembodiments of the present invention, the term “fluid solvent” may alsoapply to substances that are at, near, or above the critical temperatureand critical pressure (critical point) of that substance. It is wellknown to those having ordinary skill in the art that substances abovethe critical point of that substance are known as “supercritical fluids”which do not have the typical physical properties (i.e. density) of aliquid.

As used herein, the term “dissolved” means at least partialincorporation of a solute (polymeric or non-polymeric) in a solvent atthe molecular level. Further, the thermodynamic stability of thesolute/solvent solution can be described by the following equation 1:ΔG _(mix) =ΔH _(m) −TΔS _(mix)  (I)where ΔG_(mix) is the Gibbs free energy change of mixing of a solutewith a solvent, ΔH_(mix) is the enthalpy change of mixing, T is theabsolute temperature, and ΔS_(mix) is the entropy of mixing. To maintaina stable solution of a solute in a solvent, the Gibbs free energy mustbe negative and at a minimum. Thus, any combination of solute andsolvent that minimize a negative Gibbs free energy at appropriatetemperatures and pressures can be used for the present invention.

As used herein, the term “standard boiling point” refers to the boilingtemperature at an absolute pressure of exactly 100 kPa (1 bar, 14.5psia, 0.9869 atm) as established by the International Union of Pure andApplied Chemistry (IUPAC).

As used herein, the term “standard enthalpy change of vaporization”refers to the enthalpy change required to transform a specified quantityof a substance from a liquid into a vapor at the standard boiling pointof the substance.

As used herein, the term “polymer solution” refers to a solution ofpolymer dissolved in a solvent. The polymer solution may containundissolved matter and thus the polymer solution may also be a “slurry”of undissolved matter suspended in a solution of polymer dissolved in asolvent.

As used herein, the term “solid media” refers to a substance that existsin the solid state under the conditions of use. The solid media may becrystalline, semi-crystalline, or amorphous. The solid media may begranular and may be supplied in different shapes (i.e. spheres,cylinders, pellets, etc.). If the solid media is granular, the particlesize and particle size distribution of solid media may be defined by themesh size used to classify the granular media. An example of standardmesh size designations can be found in the American Society for Testingand Material (ASTM) standard ASTM E11 “Standard Specification for WovenWire Test Sieve Cloth and Test Sieves.” The solid media may also be anon-woven fibrous mat or a woven textile.

As used herein, the term “purer polymer solution” refers to a polymersolution having fewer contaminants relative to the same polymer solutionprior to a purification step.

As used herein, the term “virgin-like” means essentiallycontaminant-free, pigment-free, odor-free, homogenous, and similar inproperties to virgin polymers.

As used herein, the term “primarily polypropylene copolymer” refers acopolymer with greater than 70 mol % of propylene repeating units.

As used herein, the term “primarily polyethylene copolymer” refers acopolymer with greater than 70 mol % of ethylene repeating units.

II. Method for Purifying Contaminated Polymers

Surprisingly, it has been found that certain fluid solvents, which in apreferred embodiment exhibit temperature and pressure-dependentsolubility for polymers, when used in a relatively simple process can beused to purify contaminated polymers, especially reclaimed or recycledpolymers, to a near virgin-like quality. This process, exemplified inFIG. 1, comprises 1) obtaining a reclaimed polymer (step a in FIG. 1),followed by 2) extracting the polymer with a fluid solvent at anextraction temperature (T_(E)) and at an extraction pressure (P_(E))(step b in FIG. 1), followed by 3) dissolution of the polymer in a fluidsolvent at a dissolution temperature (T_(D)) and at a dissolutionpressure (P_(D)) (step c in FIG. 1), followed by 4) contacting thedissolved polymer solution with solid media at a dissolution temperature(T_(D)) and at a dissolution pressure (P_(D)) (step d in FIG. 1),followed by separation of the polymer from the fluid solvent (step e inFIG. 1). In one embodiment of the present invention, the purifiedpolymers, which may be sourced from post-consumer waste streams, areessentially contaminant-free, pigment-free, odor-free, homogenous, andsimilar in properties to virgin polymers. Furthermore, in a preferredembodiment, the physical properties of the fluid solvent of the presentinvention may enable more energy efficient methods for separation of thefluid solvent from the purified polymer.

Reclaimed Polymer

In one embodiment of the present invention, a method for purifyingreclaimed polymers includes obtaining a reclaimed polymer. For thepurposes of the present invention, the reclaimed polymer is sourced frompost-consumer, post-industrial, post-commercial, and/or other specialwaste streams. For example, post-consumer waste polymers can be derivedfrom curbside recycle streams where end-consumers place used polymersfrom packages and products into a designated bin for collection by awaste hauler or recycler. Post-consumer waste polymers can also bederived from in-store “take-back” programs where the consumer bringswaste polymers into a store and places the waste polymers in adesignated collection bin. An example of post-industrial waste polymerscan be waste polymers produced during the manufacture or shipment of agood or product that are collected as unusable material by themanufacturer (i.e. trim scraps, out of specification material, start upscrap). An example of waste polymers from a special waste stream can bewaste polymers derived from the recycling of electronic waste, alsoknown as e-waste. Another example of waste polymers from a special wastestream can be waste polymers derived from the recycling of automobiles.Another example of waste polymers from a special waste stream can bewaste polymers derived from the recycling of used carpeting andtextiles.

For the purposes of the present invention, the reclaimed polymer is ahomogenous composition of an individual polymer or a mixture of severaldifferent polymer compositions. Non-limiting examples of reclaimedpolymeric compositions are homopolymers and copolymers of polyolefins,such as polyethylene and isotactic polypropylene, polyesters, such aspoly(ethylene terephthalate), vinyl polymers, such as poly(vinylchloride), styrenic polymers, such as polystyrene, polyamides, such aspoly(hexamethylene adapamide), polycarbonates, such as poly(bisphenol-Acarbonate), polyacrylates, such as poly(methyl methacrylate),polysiloxanes, such as poly(dimethylsiloxane), thermoplastic elastomers,such as styrene-butadiene block copolymers and ethylene-propylenerubber, and other dissolvable polymers that may be apparent to thosehaving ordinary skill in the art.

The reclaimed polymer may also contain various pigments, dyes, processaides, stabilizing additives, fillers, and other performance additivesthat were added to the polymer during polymerization or conversion ofthe original polymer to the final form of an article. Non-limitingexamples of pigments are organic pigments, such as copperphthalocyanine, inorganic pigments, such as titanium dioxide, and otherpigments that may be apparent to those having ordinary skill in the art.A non-limiting example of an organic dye is Basic Yellow 51.Non-limiting examples of process aides are antistatic agents, such asglycerol monostearate and slip-promoting agents, such as erucamide. Anon-limiting example of a stabilizing additive isoctadecyl-3-(3,5-di-tert.butyl-4-hydroxyphenyl)-propionate. Non-limitingexamples of fillers are calcium carbonate, talc, and glass fibers.

Solvent

The fluid solvent of the present invention has a standard boiling pointless than about 70° C. Pressurization maintains solvents, which havestandard boiling points below the operating temperature range of thepresent invention, in a state in which there is little or no solventvapor. In one embodiment, the fluid solvent with a standard boilingpoint less than about 70° C. is selected from the group consisting ofcarbon dioxide, ketones, alcohols, ethers, esters, alkenes, alkanes, andmixtures thereof. Non-limiting examples of fluid solvents with standardboing points less than about 70° C. are carbon dioxide, acetone,methanol, dimethyl ether, diethyl ether, ethyl methyl ether,tetrahydrofuran, methyl acetate, ethylene, propylene, 1-butene,2-butene, isobutylene, 1-pentene, 2-pentene, branched isomers ofpentene, 1-hexene, 2-hexene, methane, ethane, propane, n-butane,isobutane, n-pentane, isopentane, neopentane, n-hexane, isomers ofisohexane, and other substances that may be apparent to those havingordinary skill in the art.

The selection of the appropriate solvent or solvent mixture will dependon which reclaimed polymer or polymer mixture is being purified by thepresent invention. Further, the selection of the polymer being purifiedand the corresponding fluid solvent used will dictate the temperatureand pressure ranges used to perform the steps of the present invention.A review of polymer phase behavior in solvents of the kind described bythe present invention is provided in the following reference: McHugh etal. (1999) Chem. Rev. 99:565-602.

Extraction

In one embodiment of the present invention, a method for purifyingreclaimed polymers includes contacting a reclaimed polymer with a fluidsolvent at a temperature and at a pressure wherein the polymer isessentially insoluble in the fluid solvent. Although not wishing to bebound by any theory, applicants believe that the temperature andpressure-dependent solubility can be controlled in such a way to preventthe fluid solvent from fully solubilizing the polymer, however, thefluid solvent can diffuse into the polymer and extract any extractablecontamination. The extractable contamination may be residual processingaides added to the polymer, residual product formulations whichcontacted the polymer, such as perfumes and flavors, dyes, and any otherextractable material that may have been intentionally added orunintentionally became incorporated into the polymer, for example,during waste collection and subsequent accumulation with other wastematerials.

In one embodiment, the controlled extraction may be accomplished byfixing the temperature of the polymer/fluid solvent system and thencontrolling the pressure below a pressure, or pressure range, where thepolymer dissolves in the fluid solvent. In another embodiment, thecontrolled extraction is accomplished by fixing the pressure of thepolymer/solvent system and then controlling the temperature below atemperature, or temperature range where the polymer dissolves in thefluid solvent. The temperature and pressure-controlled extraction of thepolymer with a fluid solvent uses a suitable pressure vessel and may beconfigured in a way that allows for continuous extraction of the polymerwith the fluid solvent. In one embodiment of the present invention, thepressure vessel may be a continuous liquid-liquid extraction columnwhere molten polymer is pumped into one end of the extraction column andthe fluid solvent is pumped into the same or the opposite end of theextraction column. In another embodiment, the fluid containing extractedcontamination is removed from the process. In another embodiment, thefluid containing extracted contamination is purified, recovered, andrecycled for use in the extraction step or a different step in theprocess. In one embodiment of the present invention, the extraction maybe performed as a batch method, wherein the reclaimed polymer is fixedin a pressure vessel and the fluid solvent is continuously pumpedthrough the fixed polymer phase. The extraction time or the amount offluid solvent used will depend on the desired purity of the final purerpolymer and the amount of extractable contamination in the startingreclaimed polymer. In another embodiment, the fluid containing extractedcontamination is contacted with solid media in a separate step asdescribed in the “Purification” section below. In another embodiment, amethod for purifying reclaimed polymers includes contacting a reclaimedpolymer with a fluid solvent at a temperature and at a pressure whereinthe polymer is molten and in the liquid state. In another embodiment,the reclaimed polymer is contacted with the fluid solvent at atemperature and at a pressure wherein the polymer is in the solid state.

In one embodiment, a method for purifying reclaimed polymers includescontacting polyethylene with a fluid solvent at a temperature and apressure wherein the polyethylene remains essentially undissolved. Inanother embodiment, a method for purifying reclaimed polymers includescontacting polyethylene with n-butane at a temperature from about 80° C.to about 220° C. In another embodiment, a method for purifying reclaimedpolymers includes contacting polyethylene with n-butane at a temperaturefrom about 100° C. to about 200° C. In another embodiment, a method forpurifying reclaimed polymers includes contacting polyethylene withn-butane at a temperature from about 130° C. to about 180° C. In anotherembodiment, a method for purifying reclaimed polymers includescontacting polyethylene with n-butane at a pressure from about 150 psig(1.03 MPa) to about 6,500 psig (44.82 MPa). In another embodiment, amethod for purifying reclaimed polymers includes contacting polyethylenewith n-butane at a pressure from about 3,000 psig (20.68 MPa) to about6,000 psig (41.37 MPa). In another embodiment, a method for purifyingreclaimed polymers includes contacting polyethylene with n-butane at apressure from about 4,500 psig (31.03 MPa) to about 5,500 psig (37.92MPa).

In another embodiment, a method for purifying reclaimed polymersincludes contacting polyethylene with propane at a temperature fromabout 80° C. to about 220° C. In another embodiment, a method forpurifying reclaimed polymers includes contacting polyethylene withpropane at a temperature from about 100° C. to about 200° C. In anotherembodiment, a method for purifying reclaimed polymers includescontacting polyethylene with propane at a temperature from about 130° C.to about 180° C. In another embodiment, a method for purifying reclaimedpolymers includes contacting polyethylene with propane at a pressurefrom about 1,000 psig (6.89 MPa) to about 15,000 psig (103.42 MPa). Inanother embodiment, a method for purifying reclaimed polymers includescontacting polyethylene with propane at a pressure from about 2,000 psig(13.79 MPa) to about 10,000 psig (68.95 MPa). In another embodiment, amethod for purifying reclaimed polymers includes contacting polyethylenewith n-butane at a pressure from about 5,000 psig (34.47 MPa) to about9,000 psig (62.05 MPa).

In one embodiment, a method for purifying reclaimed polymers includescontacting polypropylene with a fluid solvent at a temperature and apressure wherein the polypropylene remains essentially undissolved. Inanother embodiment, a method for purifying reclaimed polymers includescontacting polypropylene with n-butane at a temperature from about 80°C. to about 220° C. In another embodiment, a method for purifyingreclaimed polymers includes contacting polypropylene with n-butane at atemperature from about 100° C. to about 200° C. In another embodiment, amethod for purifying reclaimed polymers includes contactingpolypropylene with n-butane at a temperature from about 130° C. to about180° C. In another embodiment, a method for purifying reclaimed polymersincludes contacting polypropylene with n-butane at a pressure from about150 psig (1.03 MPa) to about 3,000 psig (20.68 MPa). In anotherembodiment, a method for purifying reclaimed polymers includescontacting polypropylene with n-butane at a pressure from about 1,000psig (6.89 MPa) to about 2,750 psig (18.96 MPa). In another embodiment,a method for purifying reclaimed polymers includes contactingpolypropylene with n-butane at a pressure from about 1,500 psig (10.34MPa) to about 2,500 psig (17.24 MPa).

In another embodiment, a method for purifying reclaimed polymersincludes contacting polypropylene with propane at a temperature fromabout 80° C. to about 220° C. In another embodiment, a method forpurifying reclaimed polymers includes contacting polypropylene withpropane at a temperature from about 100° C. to about 200° C. In anotherembodiment, a method for purifying reclaimed polymers includescontacting polypropylene with propane at a temperature from about 130°C. to about 180° C. In another embodiment, a method for purifyingreclaimed polymers includes contacting polypropylene with propane at apressure from about 200 psig (1.38 MPa) to about 8,000 psig (55.16 MPa).In another embodiment, a method for purifying reclaimed polymersincludes contacting polypropylene with propane at a pressure from about1,000 psig (6.89 MPa) to about 6,000 psig (41.37 MPa). In anotherembodiment, a method for purifying reclaimed polymers includescontacting polypropylene with propane at a pressure from about 2,000psig (13.79 MPa) to about 4,000 psig (27.58 MPa).

In one embodiment, a method for purifying reclaimed polymers includescontacting polystyrene with a fluid solvent at a temperature and apressure wherein the polystyrene remains essentially undissolved. Inanother embodiment, a method for purifying reclaimed polymers includescontacting polystyrene with n-butane at a temperature from about 90° C.to about 220° C. In another embodiment, a method for purifying reclaimedpolymers includes contacting polystyrene with n-butane at a temperaturefrom about 100° C. to about 200° C. In another embodiment, a method forpurifying reclaimed polymers includes contacting polystyrene withn-butane at a temperature from about 120° C. to about 180° C. In anotherembodiment, a method for purifying reclaimed polymers includescontacting polystyrene with n-butane at a pressure from about 500 psig(3.45 MPa) to about 5,000 psig (34.47 MPa). In another embodiment, amethod for purifying reclaimed polymers includes contacting polystyrenewith n-butane at a pressure from about 1,000 psig (6.89 MPa) to about4,000 psig (27.58 MPa). In another embodiment, a method for purifyingreclaimed polymers includes contacting polystyrene with n-butane at apressure from about 2,000 psig (13.79 MPa) to about 3,000 psig (20.68MPa).

In one embodiment, a method for purifying reclaimed polymers includescontacting poly(dimethylsiloxane) with a fluid solvent at a temperatureand a pressure wherein the poly(dimethylsiloxane) remains essentiallyundissolved. In another embodiment, a method for purifying reclaimedpolymers includes contacting poly(dimethylsiloxane) with n-butane at atemperature from about 100° C. to about 220° C. In another embodiment, amethod for purifying reclaimed polymers includes contactingpoly(dimethylsiloxane) with n-butane at a temperature from about 115° C.to about 200° C. In another embodiment, a method for purifying reclaimedpolymers includes contacting poly(dimethylsiloxane) with n-butane at atemperature from about 120° C. to about 180° C. In another embodiment, amethod for purifying reclaimed polymers includes contactingpoly(dimethylsiloxane) with n-butane at a pressure from about 200 psig(1.38 MPa) to about 1,800 psig (12.41 MPa). In another embodiment, amethod for purifying reclaimed polymers includes contactingpoly(dimethylsiloxane) with n-butane at a pressure from about 300 psig(2.07 MPa) to about 1,500 psig (10.34 MPa). In another embodiment, amethod for purifying reclaimed polymers includes contactingpoly(dimethylsiloxane) with n-butane at a pressure from about 500 psig(3.45 MPa) to about 1,000 psig (6.89 MPa).

Dissolution

In one embodiment of the present invention, a method for purifyingreclaimed polymers includes dissolving the reclaimed polymer in a fluidsolvent at a temperature and at a pressure wherein the polymer isdissolved in the fluid solvent. Although not wishing to be bound by anytheory, applicants believe that the temperature and pressure can becontrolled in such a way to enable thermodynamically favorabledissolution of the reclaimed polymer in a fluid solvent. Furthermore,the temperature and pressure can be controlled in such a way to enabledissolution of a particular polymer or polymer mixture while notdissolving other polymers or polymer mixtures. This controllabledissolution enables the separation of polymers from polymer mixtures.

In one embodiment of the present invention, a method for purifyingreclaimed polymers includes dissolving contaminated reclaimed polymersin a solvent that does not dissolve the contaminants under the sameconditions of temperature and pressure. The contaminants may includepigments, fillers, dirt, and other polymers. These contaminants arereleased from the reclaimed polymer upon dissolution and then removedfrom the polymer solution via a subsequent solid-liquid separation step.

In one embodiment of the present invention, a method for purifyingreclaimed polymers includes dissolving polyethylene in a fluid solventat a temperature and at a pressure wherein the polyethylene is dissolvedin the fluid solvent. In another embodiment, a method for purifyingreclaimed polymers includes dissolving polyethylene in n-butane at atemperature from about 90° C. to about 220° C. In another embodiment, amethod for purifying reclaimed polymers includes dissolving polyethylenein n-butane at a temperature from about 100° C. to about 200° C. Inanother embodiment, a method for purifying reclaimed polymers includesdissolving polyethylene in n-butane at a temperature from about 130° C.to about 180° C. In another embodiment, a method for purifying reclaimedpolymers includes dissolving polyethylene in n-butane at a pressure fromabout 1,000 psig (6.89 MPa) to about 12,000 psig (82.74 MPa). In anotherembodiment, a method for purifying reclaimed polymers includesdissolving polyethylene in n-butane at a pressure from about 2,000 psig(13.79 MPa) to about 10,000 psig (68.95 MPa). In another embodiment, amethod for purifying reclaimed polymers includes dissolving polyethylenein n-butane at a pressure from about 4,000 psig (27.58 MPa) to about6,000 psig (41.37 MPa).

In another embodiment, a method for purifying reclaimed polymersincludes dissolving polyethylene in propane at a temperature from about90° C. to about 220° C. In another embodiment, a method for purifyingreclaimed polymers includes dissolving polyethylene in propane at atemperature from about 100° C. to about 200° C. In another embodiment, amethod for purifying reclaimed polymers includes dissolving polyethylenein propane at a temperature from about 130° C. to about 180° C. Inanother embodiment, a method for purifying reclaimed polymers includesdissolving polyethylene in propane at a pressure from about 3,000 psig(20.68 MPa) to about 20,000 psig (137.90 MPa). In another embodiment, amethod for purifying reclaimed polymers includes dissolving polyethylenein propane at a pressure from about 5,000 psig (34.47 MPa) to about15,000 psig (103.42 MPa). In another embodiment, a method for purifyingreclaimed polymers includes dissolving polyethylene in propane at apressure from about 8,000 psig (55.16 MPa) to about 11,000 psig (75.84MPa).

In one embodiment, a method for purifying reclaimed polymers includesdissolving polypropylene in a fluid solvent at a temperature and apressure wherein the polypropylene is dissolved in the fluid solvent. Inanother embodiment, a method for purifying reclaimed polymers includesdissolving polypropylene in n-butane at a temperature from about 90° C.to about 220° C. In another embodiment, a method for purifying reclaimedpolymers includes dissolving polypropylene in n-butane at a temperaturefrom about 100° C. to about 200° C. In another embodiment, a method forpurifying reclaimed polymers includes dissolving polypropylene inn-butane at a temperature from about 130° C. to about 180° C. In anotherembodiment, a method for purifying reclaimed polymers includesdissolving polypropylene in n-butane at a pressure from about 350 psig(2.41 MPa) to about 4,000 psig (27.57 MPa). In another embodiment, amethod for purifying reclaimed polymers includes dissolvingpolypropylene in n-butane at a pressure from about 1,000 psig (6.89 MPa)to about 3,500 psig (24.13 MPa). In another embodiment, a method forpurifying reclaimed polymers includes dissolving polypropylene inn-butane at a pressure from about 2,000 psig (13.79 MPa) to about 3,000psig (20.68 MPa).

In another embodiment, a method for purifying reclaimed polymersincludes dissolving polypropylene in propane at a temperature from about90° C. to about 220° C. In another embodiment, a method for purifyingreclaimed polymers includes dissolving polypropylene in propane at atemperature from about 100° C. to about 200° C. In another embodiment, amethod for purifying reclaimed polymers includes dissolvingpolypropylene in propane at a temperature from about 130° C. to about180° C. In another embodiment, a method for purifying reclaimed polymersincludes dissolving polypropylene in propane at a pressure from about2,000 psig (13.79 MPa) to about 8,000 psig (55.16 MPa). In anotherembodiment, a method for purifying reclaimed polymers includesdissolving polypropylene in propane at a pressure from about 3,000 psig(20.68 MPa) to about 6,000 psig (41.37 MPa). In another embodiment, amethod for purifying reclaimed polymers includes dissolvingpolypropylene in propane at a pressure from about 3,500 psig (24.13 MPa)to about 5,000 psig (34.47 MPa).

In one embodiment, a method for purifying reclaimed polymers includesdissolving polystyrene in a fluid solvent at a temperature and apressure wherein the polystyrene is dissolved in the fluid solvent. Inanother embodiment, a method for purifying reclaimed polymers includesdissolving polystyrene in n-butane at a temperature from about 90° C. toabout 220° C. In another embodiment, a method for purifying reclaimedpolymers includes dissolving polystyrene in n-butane at a temperaturefrom about 100° C. to about 200° C. In another embodiment, a method forpurifying reclaimed polymers includes dissolving polystyrene in n-butaneat a temperature from about 130° C. to about 180° C. In anotherembodiment, a method for purifying reclaimed polymers includesdissolving polystyrene in n-butane at a pressure from about 1,000 psig(6.89 MPa) to about 9,000 psig (62.05 MPa). In another embodiment, amethod for purifying reclaimed polymers includes dissolving polystyrenein n-butane at a pressure from about 2,000 psig (13.79 MPa) to about8,000 psig (55.16 MPa). In another embodiment, a method for purifyingreclaimed polymers includes dissolving polystyrene in n-butane at apressure from about 4,500 psig (31.03 MPa) to about 7,500 psig (51.71MPa).

In one embodiment, a method for purifying reclaimed polymers includesdissolving poly(dimethylsiloxane) in a fluid solvent at a temperatureand a pressure wherein the poly(dimethylsiloxane) is dissolved in thefluid solvent. In another embodiment, a method for purifying reclaimedpolymers includes dissolving poly(dimethylsiloxane) in n-butane at atemperature from about 115° C. to about 220° C. In another embodiment, amethod for purifying reclaimed polymers includes dissolvingpoly(dimethylsiloxane) in n-butane at a temperature from about 120° C.to about 200° C. In another embodiment, a method for purifying reclaimedpolymers includes dissolving poly(dimethylsiloxane) in n-butane at atemperature from about 140° C. to about 180° C. In another embodiment, amethod for purifying reclaimed polymers includes dissolvingpoly(dimethylsiloxane) in n-butane at a pressure from about 500 psig(3.45 MPa) to about 2,100 psig (14.48 MPa). In another embodiment, amethod for purifying reclaimed polymers includes dissolvingpoly(dimethylsiloxane) in n-butane at a pressure from about 700 psig(4.83 MPa) to about 1,400 psig (9.65 MPa). In another embodiment, amethod for purifying reclaimed polymers includes dissolvingpoly(dimethylsiloxane) in n-butane at a pressure from about 800 psig(5.52 MPa) to about 1,300 psig (8.96 MPa).

Purification

In one embodiment of the present invention, a method for purifyingreclaimed polymers includes contacting a contaminated polymer solutionwith solid media at a temperature and at a pressure wherein the polymerremains dissolved in the fluid solvent. The solid media of the presentinvention is any solid material that removes at least some of thecontamination from a solution of reclaimed polymer dissolved in thefluid solvent of the present invention. Although not wishing to be boundby any theory, the applicants believe that solid media removescontamination by a variety of mechanisms. Non-limiting examples ofpossible mechanisms include adsorption, absorption, size exclusion, ionexclusion, ion exchange, and other mechanisms that may be apparent tothose having ordinary skill in the art. Furthermore, the pigments andother contaminants commonly found in reclaimed polymers may be polarcompounds and may preferentially interact with the solid media, whichmay also be at least slightly polar. The polar-polar interactions areespecially favorable when non-polar solvents, such as alkanes, are usedas the fluid solvent.

In one embodiment of the present invention, the solid media is selectedfrom the group consisting of inorganic substances, carbon-basedsubstances, or mixtures thereof. Useful examples of inorganic substancesinclude oxides of silicon, oxides of aluminum, oxides of iron, aluminumsilicates, magnesium silicates, amorphous volcanic glasses, silica,silica gel, diatomite, sand, quartz, reclaimed glass, alumina, perlite,fuller's earth, bentonite, and mixtures thereof. Useful examples ofcarbon-based substances include anthracite coal, carbon black, coke,activated carbon, cellulose, and mixtures thereof. In another embodimentof the present invention, the solid media is recycled glass.

In one embodiment of the present invention, the solid media is contactedwith the polymer in a vessel for a specified amount of time while thesolid media is agitated. In another embodiment, the solid media isremoved from the purer polymer solution via a solid-liquid separationstep. Non-limiting examples of solid-liquid separation steps includefiltration, decantation, centrifugation, and settling. In anotherembodiment of the present invention, the contaminated polymer solutionis passed through a stationary bed of solid media. In another embodimentof the present invention, the height or length of the stationary bed ofsolid media is greater than 5 cm. In another embodiment of the presentinvention, the height or length of the stationary bed of solid media isgreater than 10 cm. In another embodiment of the present invention, theheight or length of the stationary bed of solid media is greater than 20cm. In another embodiment of the present invention, the solid media isreplaced as needed to maintain a desired purity of polymer. In yetanother embodiment, the solid media is regenerated and re-used in thepurification step. In another embodiment, the solid media is regeneratedby fluidizing the solid media during a backwashing step.

In one embodiment, a method for purifying reclaimed polyethyleneincludes contacting a polyethylene/fluid solvent solution with solidmedia at a temperature and a pressure wherein the polyethylene remainsdissolved in the fluid solvent. In another embodiment, a method forpurifying reclaimed polymers includes contacting a polyethylene/n-butanesolution with solid media at a temperature from about 90° C. to about220° C. In another embodiment, a method for purifying reclaimed polymersincludes contacting a polyethylene/n-butane solution with solid media ata temperature from about 100° C. to about 200° C. In another embodiment,a method for purifying reclaimed polymers includes contacting apolyethylene/n-butane solution with solid media at a temperature fromabout 130° C. to about 180° C. In another embodiment, a method forpurifying reclaimed polymers includes contacting a polyethylene/n-butanesolution with solid media at a pressure from about 1,000 psig (6.89 MPa)to about 12,000 psig (82.74 MPa). In another embodiment, a method forpurifying reclaimed polymers includes contacting a polyethylene/n-butanesolution with solid media at a pressure from about 2,000 psig (13.79MPa) to about 10,000 psig (68.95 MPa). In another embodiment, a methodfor purifying reclaimed polymers includes contacting apolyethylene/n-butane solution with solid media at a pressure from about4,000 psig (27.58 MPa) to about 6,000 psig (41.37 MPa).

In another embodiment, a method for purifying reclaimed polymersincludes contacting a polyethylene/propane solution with solid media ata temperature from about 90° C. to about 220° C. In another embodiment,a method for purifying reclaimed polymers includes contacting apolyethylene/propane solution with solid media at a temperature fromabout 100° C. to about 200° C. In another embodiment, a method forpurifying reclaimed polymers includes contacting a polyethylene/propanesolution with solid media at a temperature from about 130° C. to about180° C. In another embodiment, a method for purifying reclaimed polymersincludes contacting a polyethylene/propane solution with solid media ata pressure from about 3,000 psig (20.68 MPa) to about 20,000 psig(137.90 MPa). In another embodiment, a method for purifying reclaimedpolymers includes contacting a polyethylene/propane solution with solidmedia at a pressure from about 5,000 psig (34.47 MPa) to about 15,000psig (103.42 MPa). In another embodiment, a method for purifyingreclaimed polymers includes contacting a polyethylene/propane solutionwith solid media at a pressure from about 8,000 psig (55.16 MPa) toabout 11,000 psig (75.84 MPa).

In one embodiment, a method for purifying reclaimed polypropyleneincludes contacting a polypropylene/fluid solvent solution with solidmedia at a temperature and at a pressure wherein the polypropyleneremains dissolved in the fluid solvent. In another embodiment, a methodfor purifying reclaimed polymers includes contacting apolypropylene/n-butane solution with solid media at a temperature fromabout 90° C. to about 220° C. In another embodiment, a method forpurifying reclaimed polymers includes contacting apolypropylene/n-butane solution with solid media at a temperature fromabout 100° C. to about 200° C. In another embodiment, a method forpurifying reclaimed polymers includes contacting apolypropylene/n-butane solution with solid media at a temperature fromabout 130° C. to about 180° C. In another embodiment, a method forpurifying reclaimed polymers includes contacting apolypropylene/n-butane solution with solid media at a pressure fromabout 350 psig (2.41 MPa) to about 4,000 psig (27.57 MPa). In anotherembodiment, a method for purifying reclaimed polymers includescontacting a polypropylene/n-butane solution with solid media at apressure from about 1,000 psig (6.89 MPa) to about 3,500 psig (24.13MPa). In another embodiment, a method for purifying reclaimed polymersincludes contacting a polypropylene/n-butane solution with solid mediaat a pressure from about 2,000 psig (13.79 MPa) to about 3,000 psig(20.68 MPa).

In another embodiment, a method for purifying reclaimed polymersincludes contacting a polypropylene/propane solution with solid media ata temperature from about 90° C. to about 220° C. In another embodiment,a method for purifying reclaimed polymers includes contacting apolypropylene/propane solution with solid media at a temperature fromabout 100° C. to about 200° C. In another embodiment, a method forpurifying reclaimed polymers includes contacting a polypropylene/propanesolution with solid media at a temperature from about 130° C. to about180° C. In another embodiment, a method for purifying reclaimed polymersincludes contacting a polypropylene/propane solution with solid media ata pressure from about 2,000 psig (13.79 MPa) to about 8,000 psig (55.16MPa). In another embodiment, a method for purifying reclaimed polymersincludes contacting a polypropylene/propane solution with solid media ata pressure from about 3,000 psig (20.68 MPa) to about 6,000 psig (41.37MPa). In another embodiment, a method for purifying reclaimed polymersincludes contacting a polypropylene/propane solution with solid media ata pressure from about 3,500 psig (24.13 MPa) to about 5,000 psig (34.47MPa).

In one embodiment, a method for purifying reclaimed polymers includescontacting a polystyrene/fluid solvent solution with solid media at atemperature and at a pressure wherein the polystyrene remains dissolvedin the fluid solvent. In another embodiment, a method for purifyingreclaimed polymers includes contacting a polystyrene/n-butane solutionwith solid media at a temperature from about 90° C. to about 220° C. Inanother embodiment, a method for purifying reclaimed polymers includescontacting a polystyrene/n-butane solution with solid media at atemperature from about 100° C. to about 200° C. In another embodiment, amethod for purifying reclaimed polymers includes contacting apolystyrene/n-butane solution with solid media at a temperature fromabout 130° C. to about 180° C. In another embodiment, a method forpurifying reclaimed polymers includes contacting a polystyrene/n-butanesolution with solid media at a pressure from about 1,000 psig (6.89 MPa)to about 9,000 psig (62.05 MPa). In another embodiment, a method forpurifying reclaimed polymers includes contacting a polystyrene/n-butanesolution with solid media at a pressure from about 2,000 psig (13.79MPa) to about 8,000 psig (55.16 MPa). In another embodiment, a methodfor purifying reclaimed polymers includes contacting apolystyrene/n-butane solution with solid media at a pressure from about4,500 psig (31.03 MPa) to about 7,500 psig (51.71 MPa).

In one embodiment, a method for purifying reclaimed polymers includescontacting a poly(dimethylsiloxane)/fluid solvent solution with solidmedia at a temperature and at a pressure wherein thepoly(dimethylsiloxane) remains dissolved in the fluid solvent. Inanother embodiment, a method for purifying reclaimed polymers includescontacting a poly(dimethylsiloxane)/n-butane solution with solid mediaat a temperature from about 115° C. to about 220° C. In anotherembodiment, a method for purifying reclaimed polymers includescontacting a poly(dimethylsiloxane)/n-butane solution with solid mediaat a temperature from about 120° C. to about 200° C. In anotherembodiment, a method for purifying reclaimed polymers includescontacting a poly(dimethylsiloxane)/n-butane solution with solid mediaat a temperature from about 140° C. to about 180° C. In anotherembodiment, a method for purifying reclaimed polymers includescontacting a poly(dimethylsiloxane)/n-butane solution with solid mediaat a pressure from about 500 psig (3.45 MPa) to about 2,100 psig (14.48MPa). In another embodiment, a method for purifying reclaimed polymersincludes contacting a poly(dimethylsiloxane)/n-butane solution withsolid media at a pressure from about 700 psig (4.83 MPa) to about 1,400psig (9.65 MPa). In another embodiment, a method for purifying reclaimedpolymers includes contacting a poly(dimethylsiloxane)/n-butane solutionwith solid media at a pressure from about 800 psig (5.52 MPa) to about1,300 psig (8.96 MPa).

Separation

In one embodiment of the present invention, a method for purifyingreclaimed polymers includes separating the purer polymer from the fluidsolvent at a temperature and at a pressure wherein the polymerprecipitates from solution and is no longer dissolved in the fluidsolvent. In another embodiment, the precipitation of the purer polymerfrom the fluid solvent is accomplished by reducing the pressure at afixed temperature. In another embodiment, the precipitation of the purerpolymer from the fluid solvent is accomplished by reducing thetemperature at a fixed pressure. In another embodiment, theprecipitation of the purer polymer from the fluid solvent isaccomplished by increasing the temperature at a fixed pressure. Inanother embodiment, the precipitation of the purer polymer from thefluid solvent is accomplished by reducing both the temperature andpressure. The solvent can be partially or completely converted from theliquid to the vapor phase by controlling the temperature and pressure.In another embodiment, the precipitated polymer is separated from thefluid solvent without completely converting the fluid solvent into a100% vapor phase by controlling the temperature and pressure of thesolvent during the separation step. The separation of the precipitatedpurer polymer is accomplished by any method of liquid-liquid orliquid-solid separation. Non-limiting examples of liquid-liquid orliquid-solid separations include filtration, decantation,centrifugation, and settling.

In one embodiment, a method for purifying reclaimed polyethyleneincludes separating polyethylene from a polyethylene/fluid solventsolution at a temperature and a pressure wherein the polyethyleneprecipitates from solution. In another embodiment, a method forpurifying reclaimed polymers includes separating polyethylene from apolyethylene/n-butane solution at a temperature from about 0° C. toabout 220° C. In another embodiment, a method for purifying reclaimedpolymers includes separating polyethylene from a polyethylene/n-butanesolution at a temperature from about 50° C. to about 175° C. In anotherembodiment, a method for purifying reclaimed polymers includesseparating polyethylene from a polyethylene/n-butane solution at atemperature from about 100° C. to about 160° C. In another embodiment, amethod for purifying reclaimed polymers includes separating polyethylenefrom a polyethylene/n-butane solution at a pressure from about 0 psig (0MPa) to about 4,000 psig (27.58 MPa). In another embodiment, a methodfor purifying reclaimed polymers includes separating polyethylene from apolyethylene/n-butane solution at a pressure from about 50 psig (0.34MPa) to about 2,000 psig (13.79 MPa). In another embodiment, a methodfor purifying reclaimed polymers includes separating polyethylene from apolyethylene/n-butane solution at a pressure from about 75 psig (0.52MPa) to about 1,000 psig (6.89 MPa).

In another embodiment, a method for purifying reclaimed polymersincludes separating polyethylene from a polyethylene/propane solution ata temperature from about −42° C. to about 220° C. In another embodiment,a method for purifying reclaimed polymers includes separatingpolyethylene from a polyethylene/propane solution at a temperature fromabout 0° C. to about 150° C. In another embodiment, a method forpurifying reclaimed polymers includes separating polyethylene from apolyethylene/propane solution at a temperature from about 50° C. toabout 130° C. In another embodiment, a method for purifying reclaimedpolymers includes separating polyethylene from a polyethylene/propanesolution at a pressure from about 0 psig (0 MPa) to about 15,000 psig(103.42 MPa). In another embodiment, a method for purifying reclaimedpolymers includes separating polyethylene from a polyethylene/propanesolution at a pressure from about 50 psig (0.34 MPa) to about 5,000 psig(34.47 MPa). In another embodiment, a method for purifying reclaimedpolymers includes separating polyethylene from a polyethylene/propanesolution at a pressure from about 75 psig (0.52 MPa) to about 1,000 psig(6.89 MPa).

In one embodiment, a method for purifying reclaimed polymers includesseparating polypropylene from a polypropylene/fluid solvent solution ata temperature and at a pressure wherein the polypropylene precipitatesfrom solution. In another embodiment, a method for purifying reclaimedpolymers includes separating polypropylene from a polypropylene/n-butanesolution at a temperature from about 0° C. to about 220° C. In anotherembodiment, a method for purifying reclaimed polymers includesseparating polypropylene from a polypropylene/n-butane solution at atemperature from about 100° C. to about 200° C. In another embodiment, amethod for purifying reclaimed polymers includes separatingpolypropylene from a polypropylene/n-butane solution at a temperaturefrom about 130° C. to about 180° C. In another embodiment, a method forpurifying reclaimed polymers includes separating polypropylene from apolypropylene/n-butane solution at a pressure from about 0 psig (0 MPa)to about 2,000 psig (13.79 MPa). In another embodiment, a method forpurifying reclaimed polymers includes separating polypropylene from apolypropylene/n-butane solution at a pressure from about 50 psig (0.34MPa) to about 1,500 psig (10.34 MPa). In another embodiment, a methodfor purifying reclaimed polymers includes separating polypropylene froma polypropylene/n-butane solution at a pressure from about 75 psig (0.52MPa) to about 1,000 psig (6.89 MPa).

In another embodiment, a method for purifying reclaimed polymersincludes separating polypropylene from a polypropylene/propane solutionat a temperature from about −42° C. to about 220° C. In anotherembodiment, a method for purifying reclaimed polymers includesseparating polypropylene from a polypropylene/propane solution at atemperature from about 0° C. to about 150° C. In another embodiment, amethod for purifying reclaimed polymers includes separatingpolypropylene from a polypropylene/propane solution at a temperaturefrom about 50° C. to about 130° C. In another embodiment, a method forpurifying reclaimed polymers includes separating polypropylene from apolypropylene/propane solution at a pressure from about 0 psig (0 MPa)to about 6,000 psig (41.37 MPa). In another embodiment, a method forpurifying reclaimed polymers includes separating polypropylene from apolypropylene/propane solution at a pressure from about 50 psig (0.34MPa) to about 3,000 psig (20.68 MPa). In another embodiment, a methodfor purifying reclaimed polymers includes separating polypropylene froma polypropylene/propane solution at a pressure from about 75 psig (0.52MPa) to about 1,000 psig (6.89 MPa).

In one embodiment, a method for purifying reclaimed polymers includesseparating polystyrene from a polystyrene/fluid solvent solution at atemperature and at a pressure wherein the polystyrene precipitates fromsolution. In another embodiment, a method for purifying reclaimedpolymers includes separating polystyrene from a polystyrene/n-butanesolution at a temperature from about 0° C. to about 220° C. In anotherembodiment, a method for purifying reclaimed polymers includesseparating polystyrene from a polystyrene/n-butane solution at atemperature from about 100° C. to about 200° C. In another embodiment, amethod for purifying reclaimed polymers includes separating polystyrenefrom a polystyrene/n-butane solution at a temperature from about 130° C.to about 180° C. In another embodiment, a method for purifying reclaimedpolymers includes separating polystyrene from a polystyrene/n-butanesolution at a pressure from about 0 psig (0 MPa) to about 2,000 psig(13.79 MPa). In another embodiment, a method for purifying reclaimedpolymers includes separating polystyrene from a polystyrene/n-butanesolution at a pressure from about 50 psig (0.34 MPa) to about 1,500 psig(10.34 MPa). In another embodiment, a method for purifying reclaimedpolymers includes separating polystyrene from a polystyrene/n-butanesolution at a pressure from about 75 psig (0.52 MPa) to about 1,000 psig(6.89 MPa).

In one embodiment, a method for purifying reclaimed polymers includesseparating poly(dimethylsiloxane) from a poly(dimethylsiloxane)/fluidsolvent solution at a temperature and at a pressure wherein thepoly(dimethylsiloxane) precipitates from solution. In anotherembodiment, a method for purifying reclaimed polymers includesseparating poly(dimethylsiloxane) from a poly(dimethylsiloxane)/n-butanesolution at a temperature from about 0° C. to about 220° C. In anotherembodiment, a method for purifying reclaimed polymers includesseparating poly(dimethylsiloxane) from a poly(dimethylsiloxane)/n-butanesolution at a temperature from about 115° C. to about 200° C. In anotherembodiment, a method for purifying reclaimed polymers includesseparating poly(dimethylsiloxane) from a poly(dimethylsiloxane)/n-butanesolution at a temperature from about 120° C. to about 180° C. In anotherembodiment, a method for purifying reclaimed polymers includesseparating poly(dimethylsiloxane) from a poly(dimethylsiloxane)/n-butanesolution at a pressure from about 0 psig (0 MPa) to about 1,500 psig(10.34 MPa). In another embodiment, a method for purifying reclaimedpolymers includes separating poly(dimethylsiloxane) from apoly(dimethylsiloxane)/n-butane solution at a pressure from about 50psig (0.34 MPa) to about 1,000 psig (6.89 MPa). In another embodiment, amethod for purifying reclaimed polymers includes separatingpoly(dimethylsiloxane) from a poly(dimethylsiloxane)/n-butane solutionat a pressure from about 75 psig (0.52 MPa) to about 500 psig (3.45MPa).

III Test Methods

The test methods described herein are used to measure the effectivenessof various methods for purifying polymers. Specifically, the methodsdescribed demonstrate the effectiveness of a given purification methodat improving color and translucency/clarity (i e making the color andopacity of the reclaimed polymer closer to that of an uncolored virginpolymer), reducing or eliminating elemental contamination (i.e. removingheavy metals), reducing or eliminating non-combustible contamination(i.e. inorganic fillers), reducing or eliminating volatile compounds(especially volatile compounds that contribute to the malodor ofreclaimed polymers), and reducing or eliminating polymeric contamination(i.e. polyethylene contamination in polypropylene).

Color and Opacity Measurement:

The color and opacity/translucency of a polymer are important parametersthat determine whether or not a polymer can achieve the desired visualaesthetics of an article manufactured from the polymer. Reclaimedpolymers, especially post-consumer derived reclaimed polymers, aretypically dark in color and opaque due to residual pigments, fillers,and other contamination. Thus, color and opacity measurements areimportant parameters in determining the effectiveness of a method forpurifying polymers.

Prior to color measurement, samples of either polymeric powders orpellets were compression molded into 30 mm wide×30 mm long×1 mm thicksquare test specimens (with rounded corners). Powder samples were firstdensified at room temperature (ca. 20-23° C.) by cold pressing thepowder into a sheet using clean, un-used aluminum foil as acontact-release layer between stainless steel platens. Approximately0.85 g of either cold-pressed powder or pellets was then pressed intotest specimens on a Carver Press Model C (Carver, Inc., Wabash, IN46992-0554 USA) pre-heated to 200° C. using aluminum platens, unusedaluminum foil release layers, and a stainless steel shim with a cavitycorresponding to aforementioned dimensions of the square test specimens.Samples were heated for 5 minutes prior to applying pressure. After 5minutes, the press was then compressed with at least 2 tons (1.81 metrictons) of hydraulic pressure for at least 5 seconds and then released.The molding stack was then removed and placed between two thick flatmetal heat sinks for cooling. The aluminum foil contact release layerswere then peeled from the sample and discarded. The flash around thesample on at least one side was peeled to the mold edge and then thesample was pushed through the form. Each test specimen was visuallyevaluated for voids/bubble defects and only samples with no defects inthe color measurement area (0.7″ (17.78 mm) diameter minimum) were usedfor color measurement.

The color of each sample was characterized using the InternationalCommission on Illumination (CIE) L*, a*, b* three dimensional colorspace. The dimension L* is a measure of the lightness of a sample, withL*=0 corresponding to the darkest black sample and L*=100 correspondingto the brightest white sample. The dimension a* is a measure of the redor green color of a sample with positive values of a* corresponding witha red color and negative values of a* corresponding with a green color.The dimension b* is a measure of the blue or yellow color of a samplewith positive values of b* corresponding with a blue color and negativevalues of b* corresponding with a yellow color. The L* a*b* values ofeach 30 mm wide×30 mm long×1 mm thick square test specimen sample weremeasured on a HunterLab model LabScan XE spectrophotometer (HunterAssociates Laboratory, Inc., Reston, Va. 20190-5280, USA). Thespectrophotometer was configured with D65 as the standard illuminant, anobserver angle of 10°, an area diameter view of 1.75″ (44.45 mm), and aport diameter of 0.7″ (17.78 mm)

The opacity of each sample, which is a measure of how much light passesthrough the sample (i.e. a measure of the sample's translucency), wasdetermined using the aforementioned HunterLab spectrophotometer usingthe contrast ratio opacity mode. Two measurements were made to determinethe opacity of each sample. One to measure the brightness value of thesample backed with a white backing, Y_(WhiteBacking), and one to measurethe brightness value of the sample backed with a black backing,Y_(BlackBacking). The opacity was then calculated from the brightnessvalues using the following equation 2:

$\begin{matrix}{{\%\mspace{14mu}{Opacity}} = {\frac{Y_{{Black}\mspace{14mu}{Backing}}}{Y_{{White}\mspace{14mu}{Backing}}}*100}} & ({II})\end{matrix}$Elemental Analysis:

Many reclaimed polymers have unacceptably high concentrations of heavymetal contamination. The presence of heavy metals, for example lead,mercury, cadmium, and chromium, may prevent the use of reclaimedpolymers in certain applications, such as food or drug contactapplications or medical device applications. Thus, measuring theconcentration of heavy metals is important when determining theeffectiveness of a method for purifying polymers.

Elemental analysis was performed using Inductively Coupled Plasma MassSpectrometry (ICP-MS). Test solutions were prepared in n=2 to n=6depending on sample availability by combing ˜0.25 g sample with 4 mL ofconcentrated nitric acid and 1 mL of concentrated hydrofluoric acid(HF). The samples were digested using an Ultrawave Microwave Digestionprotocol consisting of a 20 min ramp to 125° C., a 10 min ramp to 250°C. and a 20 min hold at 250° C. Digested samples were cooled to roomtemperature. The digested samples were diluted to 50 mL after adding0.25 mL of 100 ppm Ge and Rh as the internal standard. In order toassess accuracy of measurement, pre-digestion spikes were prepared byspiking virgin polymer. Virgin polymer spiked samples were weighed outusing the same procedure mentioned above and spiked with the appropriateamount of each single element standard of interest, which included thefollowing: Na, Al, Ca, Ti, Cr, Fe, Ni, Cu, Zn, Cd, and Pb. Spikes wereprepared at two different levels: a “low level spike” and a “high levelspike”. Each spike was prepared in triplicate. In addition to spikingvirgin polymer, a blank was also spiked to verify that no errorsoccurred during pipetting and to track recovery through the process. Theblank spiked samples were also prepared in triplicate at the twodifferent levels and were treated in the same way as the spiked virginpolymer and the test samples. A 9 point calibration curve was made bymaking 0.05, 0.1, 0.5, 1, 5, 10, 50, 100, and 500 ppb solutionscontaining Na, Al, Ca, Ti, Cr, Fe, Ni, Cu, Zn, Cd, and Pb. Allcalibration standards were prepared by dilution of neat standardreference solutions and 0.25 mL of 100 ppm Ge and Rh as the internalstandard with 4 mL of concentrated nitric and 1 mL of concentrated HF.Prepared standards, test samples, and spiked test samples were analyzedusing an Agilent's 8800 ICP-QQQMS, optimized according to manufacturerrecommendations. The monitored m/z for each analyte and the collisioncell gas that was used for analysis was as follows: Na, 23 m/z, H₂; Al,27 m/z, H₂; Ca, 40 m/z, H₂; Ti, 48 m/z, H₂; Cr, 52 m/z, He; Fe, 56 m/z,H₂; Ni, 60 m/z; no gas; Cu, 65 m/z, no gas; Zn, 64 m/z, He; Cd, 112 m/z;H₂; Pb, sum of 206≥206, 207≥207, 208≥208 m/z, no gas; Ge, 72 m/z, allmodes; Rh, 103 m/z, all modes. Ge was used as an internal standard forall elements <103 m/z and Rh was used for all elements >103 m/z.

Residual Ash Content:

Many reclaimed polymers contain various fillers, for example calciumcarbonate, talcum, and glass fiber. While useful in the originalapplication of the reclaimed polymer, these fillers alter the physicalproperties of a polymer in way that may be undesired for the nextapplication of the reclaimed polymer. Thus, measuring the amount offiller is important when determining the effectiveness of a method forpurifying polymers.

Thermogravimetric analysis (TGA) was performed to quantify the amount ofnon-combustible materials in the sample (also sometimes referred to asAsh Content). About 5-15 mg of sample was loaded onto a platinum samplepan and heated to 700° C. at a rate of 20° C./min in an air atmospherein a TA Instruments model Q500 TGA instrument. The sample was heldisothermal for 10 min at 700° C. The percentage residual mass wasmeasured at 700° C. after the isothermal hold.

Odor Analysis:

Odor sensory analysis was performed by placing about 3 g of each samplein a 20 mL glass vial and equilibrating the sample at room temperaturefor at least 30 min. After equilibration, each vial was opened and theheadspace was sniffed (bunny sniff) by a trained grader to determineodor intensity and descriptor profile. Odor intensity was gradedaccording to the following scale:

5=Very Strong

4=Strong

3=Moderate

2=Weak to Moderate

1=Weak

0=No odor

Polymeric Contamination Analysis:

Many reclaimed polymers, especially reclaimed polymers originating frommixed-stream sources, may contain undesired polymeric contamination.Without wishing to be bound by any theory, polymeric contamination, forexample polyethylene contamination in polypropylene, may influence thephysical properties of the polymer due to the presence of heterogeneousphases and the resulting weak interfaces. Furthermore, the polymericcontamination may also increase the opacity of the polymer and have aninfluence on the color. Thus, measuring the amount of polymericcontamination is important when determining the effectiveness of amethod for purifying polymers.

Semi-crystalline polymeric contamination was evaluated usingDifferential Scanning calorimetry (DSC). For example, to measure theamount of polyethylene contamination in polypropylene, a set of fivepolypropylene/polyethylene blends were prepared with 2, 4, 6, 8, and 10wt % of Formolene® HB5502F HDPE (Formosa Plastics Corporation, USA) inPro-fax 6331 polypropylene (LyondellBasell Industries Holdings, B.V.).Approximately 5-15 mg of each sample was sealed in an aluminum DSC panand analyzed on a TA Instruments model Q2000 DSC with the followingmethod:

-   -   1. Equilibrate at 30.00° C.    -   2. Ramp 20.00° C./min to 200.00° C.    -   3. Mark end of cycle 0    -   4. Ramp 20.00° C./min to 30.00° C.    -   5. Mark end of cycle 1    -   6. Ramp 20.00° C./min to 200.00° C.    -   7. Mark end of cycle 2    -   8. Ramp 20.00° C./min to 30.00° C.    -   9. Mark end of cycle 3    -   10. Ramp 5.00° C./min to 200.00° C.    -   11. Mark end of cycle 4

The enthalpy of melting for the HDPE peak around 128° C. was calculatedfor each sample of known HDPE content using the 5.00° C./min DSCthermogram. A linear calibration curve, shown in FIG. 2, was establishedplotting enthalpy of melting versus known HDPE concentration (wt %).

Samples having unknown PE content were analyzed using the sameaforementioned DSC equipment and method. PE content was calculated usingthe aforementioned calibration curve. The specific HDPE used to generatethe calibration curve will more than likely have a different degree ofcrystallinity than the polyethylene (or polyethylene blend)contamination that may be present in a reclaimed polymer sample. Thedegree of crystallinity may independently influence the measuredenthalpy of melting for polyethylene and thus influence the resultingcalculation of polyethylene content. However, the DSC test methoddescribed herein is meant to serve as a relative metric to compare theeffectiveness of different methods to purify polymers and is not meantto be a rigorous quantification of the polyethylene content in a polymerblend. While the aforementioned method described the measurement ofpolyethylene contamination in polypropylene, this method may be appliedto measurement of other semi-crystalline polymers using differenttemperature ranges and peaks in the DSC thermogram. Furthermore,alternative methods, such as nuclear magnetic resonance (NMR)spectroscopy, may also be used to measure the amount of bothsemi-crystalline and amorphous polymeric contamination in a sample.

EXAMPLES

The following examples further describe and demonstrate embodimentswithin the scope of the present invention. The examples are given solelyfor the purpose of illustration and are not to be construed aslimitations of the present invention, as many variations thereof arepossible without departing from the spirit and scope of the invention.

Example 1

A sample of post-consumer derived recycled polypropylene mixed colorflake was sourced from a supplier of recycled resins. The post-consumerrecycled polypropylene originated from the United States and Canada. Theas-received, mixed-color flake was homogenized via compounding on aCentury/W&P ZSK30 twin screw extruder equipped with two 30 mm generalpurpose screws each with standard mixing and conveying elements. Thescrew rotation speed was about 50 rpm, the feeder throughput was about20 lbs/hour (9.07 kg/hour) and the temperature of the barrel ranged fromabout 210° C. at the die to about 150° C. at the feed throat. The graystrand exiting the extruder was cooled in a room-temperature water bath,dried with air, and chopped into pellets.

The sample was characterized using the test methods disclosed herein andthe resulting data are summarized in Table 1. The purpose of thisexample is to show the properties of a representative post-consumerderived recycled resin before purification.

The pellets and corresponding square test specimens were dark gray incolor as indicated in the L*a*b* values of the square test specimens.The opacity of the samples averaged about 100% opaque (i.e. notranslucency). A photograph of the square test specimen is shown in FIG.4 as Example 1. As shown in FIG. 4, the specimen was dark in color andlacked translucency.

This example serves as a representative baseline for heavy metalcontamination found in post-consumer derived recycled polypropylene.When compared to other examples, the heavy metal contamination was foundto be much greater in the as-received post-consumer derived recycledpolypropylene.

The samples of example 1 had ash content values that averaged to about1.2117 wt %, which also serves as a baseline for the amount ofnon-combustible substances that are often present in post-consumerderived recycled polypropylene.

This example also serves as a representative baseline for odor compoundcontamination found in post-consumer derived recycled polypropylene. Thesamples of example 1 were found to have an odor intensity of 3.75 on a 5point scale (5 being the most intense), and were described as having a“garbage”, “dusty”, or “sour” odor.

This example also serves as a representative baseline for polyethylenecontamination found in post-consumer derived recycled polypropylene. Thesamples of example 1 had polyethylene contents that averaged to about5.5 wt %.

Example 2

The sample of post-consumer derived recycled polypropylene mixed-colorflake described in Example 1 was processed using the experimentalapparatus shown in FIG. 3 and the following procedure:

-   -   1. 237 g of the mixed color flake was loaded into a 1.1 L        extraction column pressure vessel with an internal diameter (ID)        of 1.75″ (4.45 cm) and a length of 28″ (71.12 cm) that was        heated to an external skin temperature of 175° C.    -   2. Liquid n-butane solvent was pressurized to about 2,150 psig        (14.82 MPa) using a positive displacement pump and pre-heated to        a temperature of about 110° C. using two heat exchangers before        it was introduced to the bottom of the extraction column.    -   3. The fluid stream leaving the top of the extraction column was        introduced into the top of a second 0.5 L pressure vessel with        an ID of 2″ (5.08 cm) and a length of about 8.5″ (21.59 cm) that        was heated to an external skin temperature of 175° C. The second        pressure vessel contained 150 mL of silica gel (Silicycle Ultra        Pure Silica Gels, SiliaFlash GE60, Parc-Technologies, USA) that        was pre-mixed in a beaker with 150 mL of aluminum oxide        (Activated Alumina, Selexsorb CDX, 7×14, BASF, USA).    -   4. The fluid stream leaving the bottom of the second pressure        vessel was depressurized across an expansion valve into a        side-arm Erlenmeyer flask. After depressurizing the fluid stream        into the Erlenmeyer flask, the solvent vapor was vented through        the side-arm port and any liquids/solids were collected in the        flask. The n-butane solvent was eluted through the system at        2,150 psig (14.82 MPa) until no further material was observed        accumulating in the flask. 19.93 g of white solids were        collected and labeled ‘Fraction 1’.    -   5. The Erlenmeyer flask was replaced with an empty, clean flask        and the system pressure was then increased to 2,400 psig (16.55        MPa).    -   6. The system pressure was maintained at 2,400 psig (16.55 MPa)        until no further solid material was observed eluting from the        system. 89.35 g of white solids were collected and labeled        ‘Fraction 2’.    -   7. The Erlenmeyer flask was replaced with an empty, clean flask        and the system pressure was then increased to 2,500 psig (17.24        MPa).    -   8. The system pressure was maintained at 2,500 psig (17.24 MPa)        until no further solid material was observed eluting from the        system. 58.18 g of white solids were collected and labeled        ‘Fraction 3’.    -   9. The Erlenmeyer flask was replaced with an empty, clean flask        and the system pressure was then increased to 2,600 psig (17.93        MPa).    -   10. The system pressure was maintained at 2,600 psig (17.93 MPa)        until no further solid material was observed eluting from the        system. 7.29 g of white solids were collected and labeled        ‘Fraction 4’.    -   11. The Erlenmeyer flask was replaced with an empty, clean flask        and the system pressure was then increased to 3,000 psig (20.68        MPa).    -   12. The system pressure was maintained at 3,000 psig (20.68 MPa)        until no further solid material was observed eluting from the        system. 5.58 g of off-white solids were collected and labeled        ‘Fraction 5’.    -   13. The samples collected in each flask were allowed to degas at        room temperature and pressure for at least two days before being        characterized using the test methods disclosed herein.

The data for the white solid material collected at 2,400 psig (16.55MPa) as Fraction 2 are summarized in Table 1.

TABLE 1 Color, contamination, and odor removal of Examples 1-4 Example 1Example 2 Example 3 Example 4 Fraction N/A Fraction 2 Fraction 2Fraction 1 Solid Media N/A 150 mL of 150 mL of 150 mL of silica gelsilica gel silica gel mixed mixed mixed with with with 150 mL of 150 mLof 150 mL of aluminum aluminum aluminum oxide oxide oxide Color L* 39.76± 85.29 ± 84.57 ± 82.18 ± 0.24 0.17 0.39 0.99 (n = 3) (n = 3) (n = 3) (n= 3) Color a* −2.51 ± −0.69 ± −0.68 ± −0.93 ± 0.04 0.02 0.04 0.14 (n =3) (n = 3) (n = 3) (n = 3) Color b* −1.20 ± 2.27 ± 3.08 ± 3.40 ± 0.110.08 0.10 0.48 (n = 3) (n = 3) (n = 3) (n = 3) Opacity (Y) 100.19 ± 7.90± 9.58 ± 22.18 ± 0.15 0.19 0.94 6.93 (n = 3) (n = 3) (n = 3) (n = 3) Na(ppb) 136,000 ± 2,630 ± 36,100 ± 2,790 ± LOQ = 100 ppb 109,000 313017,300 1140 (n = 6) (n = 5) (n = 6) (n = 6) Al (ppb) 192,000 ± <LOQ50,800 ± 3,160 ± LOQ = 1000 ppb 17,300 17,300 1,710 (n = 6) (n = 6) (n =6) Ca (ppb) 1,590,000 ± 2,680 ± 13,100 ± 4,710 ± LOQ = 1000 ppb 79,5002,439 4,580 1,650 (n = 6) (n = 5) (n = 6) (n = 6) Ti (ppb) 2,800,000 ±638 ± 755 ± 9,710 ± LOQ = 100 ppb 28,000 70 219 6,210 (n = 6) (n = 5) (n= 6) (n = 6) Cr (ppb) 4,710 ± 17.5 ± 130 ± 97.7 ± LOQ = 10 ppb 612 20.549 89.9 (n = 6) (n = 5) (n = 6) (n = 6) Fe (ppb) 108,000 ± <LOQ <LOQ1,300 ± LOQ = 1000 ppb 1,080 1,300 (n = 6) (n = 6) Ni (ppb) 1,160 ± 10.9± 59.8 ± 45.4 ± LOQ = 10 ppb 151 7.3 23.3 49.9 (n = 6) (n = 5) (n = 6)(n = 6) Cu (ppb) 15,300 ± 33.0 ± 32.7 ± 242 ± LOQ = 10 ppb 612 17.2 13.799.2 (n = 6) (n = 5) (n = 6) (n = 6) Zn (ppb) 71,000 ± 261 ± 622 ± 1,060± LOQ = 10 ppb 1,420 183 454 519 (n = 6) (n = 5) (n = 6) (n = 6) Cd(ppb) 1,620 ± <LOQ <LOQ 10.8 ± LOQ = 10 ppb 113 7.24 (n = 6) (n = 6) Pb(ppb) 12,166 ± <LOQ <LOQ 80.0 ± LOQ = 10 ppb 243 43.2 (n = 6) (n = 6)Ash Content 1.2117 ± 0.2897 ± 0.1614 ± 0.2812 ± (% res from 0.15010.1533 0.0833 0.1342 TGA) (n = 3) (n = 3) (n = 3) (n = 3) Odor Intensity3.75 0.5 3 2.25 (0-5) Odor garbage, plastic, plastic, minty/ Descriptordusty, sour gasoline solvent camphor, sour, plastic, burnt PE content5.5 ± <LOQ <LOQ 1.9 ± (wt %) 0.3% 0.6% DSC method (n = 3) (n = 3) LOQ =1%

TABLE 2 Color, contamination, and odor removal of Examples 5-8 Example 5Example 6 Example 7 Example 8 Fraction Fraction 2 Fractions Fraction 2N/A 1 & 2 from Example 3 combined Solid Media 180 mL of 150 mL of NoneFuller's silica gel silica gel Earth mixed with 150 mL of aluminum oxideColor L* 82.00 ± 84.51 ± 50.51 ± 63.15 0.82 0.21 0.49 (n = 1) (n = 3) (n= 3) (n = 3) Color a* −0.84 ± −0.82 ± −3.09 ±  0.27 0.09 0.07 0.14 (n= 1) (n = 3) (n = 3) (n = 3) Color b* 3.40 ± 3.00 ± 10.23 ±  5.79 0.130.22 1.61 (n = 1) (n = 3) (n = 3) (n = 3) Opacity (Y) 18.63 ± 9.14 ±87.20 ± 24.96 2.04 0.47 2.01 (n = 1) (n = 3) (n = 3) (n = 3) Na (ppb)2,960 ± 19,700 ± 33,300 ± 5,120 ± LOQ = 100 ppb 829 11,600 4660 410 (n =5) (n = 6) (n = 3) (n = 2) Al (ppb) 2,070 ± 3,610 ± 43,500 ± 109,000 ±LOQ = 1000 ppb 124 1,910 1740 2,180 (n = 5) (n = 6) (n = 3) (n = 2) Ca(ppb) 2,740 ± 8,490 ± 13,100 ± 15,600 ± LOQ = 1000 ppb 493 4,670 4590312 (n = 5) (n = 6) (n = 3) (n = 2) Ti (ppb) 10,400 ± 2,180 ± 864,000 ±64,100 ± LOQ = 100 ppb 936 1,110 25,900 135 (n = 5) (n = 6) (n = 3) (n =2) Cr (ppb) 47.6 ± 239 ± 996 ± 757 ± LOQ = 10 ppb 28.6 206 189 204 (n =5) (n = 6) (n = 3) (n = 2) Fe (ppb) <LOQ 1,040 ± 19,300 ± 55,700 ± LOQ =1000 ppb 967 965 557 (n = 6) (n = 3) (n = 2) Ni (ppb) 38.6 ± 208 ± 148 ±218 ± LOQ = 10 ppb 33.2 245 20.7 0.196 (n = 5) (n = 6) (n = 3) (n = 2)Cu (ppb) 64.7 ± 144 ± 2,890 ± 639 ± LOQ = 10 ppb 4.53 232 86.7 345 (n =5) (n = 6) (n = 3) (n = 2) Zn (ppb) 803 ± 652 ± 19,600 ± 2,950 ± LOQ =10 ppb 88.3 267 7250 443 (n = 5) (n = 6) (n = 3) (n = 2) Cd (ppb) 13.0 ±<LOQ 389 ± 30.7 ± LOQ = 10 ppb 6.50 121 1.23 (n = 5) (n = 3) (n = 2) Pb(ppb) 118 ± 24.0 ± 1,310 ± 121 ± LOQ = 10 ppb 135 13.0 236 0.061 (n = 5)(n = 6) (n = 3) (n = 2) Ash Content 0.5723 ± 0.4951 ± 0.3154 ± 0.3294 ±(% res 0.0610 0.2448 0.0024 0.0948 from TGA) (n = 3) (n = 3) (n = 3) (n= 3) Odor Intensity 4 3.75 1 5   (0-5) Odor dirty, chlorine, plastic,gasoline Descriptor oily, plastic, petroleum minty/ oily, camphor greasyPE content 1.7 ± <LOQ 1.2 ± 5.5 ± (wt %) 0.3% 0.1% 0.1% DSC method (n =3) (n = 3) (n = 3) LOQ = 1%

The solids isolated in fractions 1-5 in this example were white incolor. When the white solids from fraction 2 were compression moldedinto square test specimens, the specimens were colorless and clear andsimilar in appearance to virgin polypropylene. A photograph of thesquare test specimen is shown in FIG. 4 as Example 2. As shown in FIG.4, the specimen was clear and comparable in color and translucency tovirgin polypropylene. The L*a*b* values showed that the square testspecimens were essentially colorless and showed a dramatic improvementin color relative to the square test specimens of example 1 (i.e.as-received post-consumer derived polypropylene). The L* values for thesquare test specimens from fraction 2 of example 2 averaged 85.29 whichwere much improved when compared to the L* values for the square testspecimens of example 1, which averaged 39.76. The opacity for the squaretest specimens from fraction 2 of example 2, which averaged 7.90% opaque(i.e. about 92% translucent), were also much improved when compared tothe opacity values for the square test specimens of example 1, whichaveraged about 100% opaque.

The concentration of heavy metal contamination for the samples fromfraction 2 of example 2 were also much improved when compared to thesamples of example 1. For example, the concentration of sodium in thesamples from fraction 2 of example 2 averaged only 2,630 ppb while theconcentration of sodium in the samples of example 1 averaged 136,000 ppb(a reduction of about 98%). The concentrations of aluminum, iron,cadmium, and lead were all below the limit of quantitation for thesamples from fraction 2 of example 2 while the concentration of the sameelements in the samples of example 1 averaged 192,000, 108,000, 1,620,and 12,166 ppb, respectively. The concentrations of all of the otherelements measured (calcium, titanium, chromium, nickel, copper, andzinc) were all reduced by greater than 99% for the samples from fraction2 of example 2 relative to the samples of example 1.

The samples from fraction 2 of example 2 had ash content values thataveraged to about 0.2897 wt %, which were significantly lower than theash content values for the samples of example 1, which averaged to about1.2117 wt %.

The samples from fraction 2 of example 2 were found to have an odorintensity of 0.5 on a 5 point scale (5 being most intense), which wasmuch improved when compared to the odor intensity of the samples ofexample 1, which had an odor intensity of 3.75. Though low in odorintensity, the samples from fraction 2 of example 2 were described ashaving a “plastic” or “gasoline” like odor similar to virginpolypropylene.

Any polyethylene content in the samples from fraction 2 of example 2 wasbelow the limit of quantitation, which was much improved when comparedto the polyethylene content of the samples of example 1, which averagedto about 5.5 wt %.

FIG. 5 is a bar chart of the opacity and odor intensity of the purifiedrecycled polypropylene of example 2 compared to the untreated recycledpolypropylene (example 1), the recycled polypropylene treated accordingto method disclosed in EP0849312 A1 (example 8), and a virginpolypropylene comparative sample. As shown in FIG. 5, the purifiedrecycled polypropylene of example 2 had both a low opacity and a lowodor intensity and was similar to the virgin polypropylene comparativesample.

Example 3

The sample of post-consumer derived recycled polypropylene mixed colorflake described in Example 1 was processed using the experimentalapparatus shown in FIG. 3 and the following procedure:

-   -   1. 225 g of the mixed color flake was loaded into a 1.1 L        extraction column pressure vessel with an internal diameter (ID)        of 1.75″ (44.45 mm) and a length of 28″ (71.12 cm) that was        heated to an external skin temperature of 135° C.    -   2. Liquid n-butane solvent was pressurized to about 1,000 psig        (6.89 MPa) using a positive displacement pump and pre-heated to        a temperature of about 90° C. using two heat exchangers before        it was introduced to the bottom of the extraction column.    -   3. The fluid stream leaving the top of the extraction column was        introduced into the top of a second 0.5 L pressure vessel with        an ID of 2″ (5.08 cm) and a length of about 8.5″ (21.59 cm) that        was heated to an external skin temperature of 135° C. The second        pressure vessel contained 150 mL of silica gel (Silicycle Ultra        Pure Silica Gels, SiliaFlash GE60, Parc-Technologies, USA) that        was pre-mixed in a beaker with 150 mL of aluminum oxide        (Activated Alumina, Selexsorb CDX, 7×14, BASF, USA).    -   4. The fluid stream leaving the bottom of the second pressure        vessel was depressurized across an expansion valve into a        side-arm Erlenmeyer flask. After depressurizing the fluid stream        into the Erlenmeyer flask, the solvent vapor was vented through        the side-arm port and any liquids/solids collected in the flask.        The n-butane solvent was eluted through the system at 1,000 psig        (6.89 MPa) until no further material was observed accumulating        in the flask. 27.52 g of off-white solids were collected and        labeled ‘Fraction 1’.    -   5. The Erlenmeyer flask was replaced with an empty, clean flask        and the system pressure was then increased to 1,500 psig (10.34        MPa).    -   6. The system pressure was maintained at 1,500 psig (10.34 MPa)        until no further solid material was observed eluting from the        system. 59.25 g of off-white solids were collected and labeled        ‘Fraction 2’.    -   7. The fraction 2 sample collected at 1,500 psig (10.34 MPa) was        then allowed to degas at room temperature and pressure for at        least two days before it was characterized using the test        methods disclosed herein.

The data for the fraction 2 sample collected at 1,500 psig (10.34 MPa)are summarized in Table 1.

The solids isolated in fraction 2 in this example were slightlyoff-white in color. When these solids were compression molded intosquare test specimens, the specimens from fraction 2 were nearlycolorless and clear and almost similar in appearance to virginpolypropylene. A photograph of the square test specimen is shown in FIG.4 as Example 3. As shown in FIG. 4, the specimen was clear andcomparable in color and translucency to virgin polypropylene. The L*a*b*values also showed that the square test specimens from fraction 2 wereessentially colorless and showed a dramatic improvement in colorrelative to the square test specimens of example 1 (i.e. as-receivedpost-consumer derived polypropylene). The L* values for the square testspecimens from fraction 2 of example 3 averaged 84.57 which were muchimproved when compared to the L* values for the square test specimens ofexample 1, which averaged 39.76. The opacity for the square testspecimens from fraction 2 of example 3, which averaged 9.58% opaque(i.e. about 90% translucent), were also much improved when compared tothe opacity values for the square test specimens of example 1, whichaveraged about 100% opaque.

The concentration of heavy metal contamination for the samples fromfraction 2 of example 3 were also much improved when compared to thesamples of example 1. For example, the concentrations of sodium in thesamples from fraction 2 of example 3 averaged 36,100 ppb while theconcentrations of sodium in the samples of example 1 averaged 136,000ppb (a reduction of about 74%). The concentrations of iron, cadmium, andlead were all below the limit of quantitation for the samples fromfraction 2 of example 3 while the concentrations of the same elements inthe samples of example 1 averaged 108,000, 1,620, and 12,166 ppb,respectively. The concentrations of calcium, titanium, chromium, nickel,copper, and zinc were all reduced by greater than 95% for the samplesfrom fraction 2 of example 3 relative to the samples of example 1. Theconcentration of aluminum was reduced by about 74% in the samecomparison.

The samples from fraction 2 of example 3 had ash content values thataveraged to about 0.1614 wt %, which was significantly lower than theash content values for the samples of example 1, which averaged to about1.2117 wt %.

The samples from fraction 2 of example 3 were found to have an odorintensity of 3 on a 5 point scale (5 being most intense), which wasslightly improved when compared to the odor intensity of the samples ofexample 1, which had an odor intensity of 3.75. The samples fromfraction 2 of example 3 had an odor described as being like “plastic” or“solvent.”

Any polyethylene content in the samples from fraction 2 of example 3 wasbelow the limit of quantitation, which was much improved when comparedto the polyethylene content of the samples of example 1, which averagedto about 5.5 wt %.

Example 4

The sample of post-consumer derived recycled polypropylene mixed colorflake described in Example 1 was processed using the experimentalapparatus shown in FIG. 3 and the following procedure:

-   -   1. 236 g of the mixed color flake was loaded into a 1.1 L        extraction column pressure vessel with an internal diameter (ID)        of 1.75″ (44.45 mm) and a length of 28″ (71.12 cm) that was        heated to an external skin temperature of 175° C.    -   2. Liquid hexanes (mixed isomers) solvent was pressurized to        about 200 psig (1.38 MPa) using a positive displacement pump and        pre-heated to a temperature of about 110° C. using two heat        exchangers before it was introduced to the bottom of the        extraction column.    -   3. The fluid stream leaving the top of the extraction column was        introduced into the top of a second 0.5 L pressure vessel with        an ID of 2″ (50.8 mm) a length of about 8.5″ (21.59 cm) that was        heated to an external skin temperature of 175° C. The second        pressure vessel contained 150 mL of silica gel (Silicycle Ultra        Pure Silica Gels, SiliaFlash GE60, Parc-Technologies, USA) that        was pre-mixed in a beaker with 150 mL of aluminum oxide        (Activated Alumina, Selexsorb CDX, 7×14, BASF, USA).    -   4. The fluid stream leaving the bottom of the second pressure        vessel was depressurized across an expansion valve into a        side-arm Erlenmeyer flask. After depressurizing the fluid stream        into the Erlenmeyer flask, the liquids/solids solution was        collected in the flask. The hexanes solvent was eluted through        the system at 200 psig (1.38 MPa) until no further material was        observed accumulating in the flask. 102.11 g of off-white solids        were collected (after solvent evaporation) and labeled ‘Fraction        1’.    -   5. The Erlenmeyer flask was replaced with an empty, clean flask        and the system pressure was then increased to 300 psig (2.07        MPa).    -   6. The system pressure was maintained at 300 psig (2.07 MPa)        until no further solid material was observed eluting from the        system. 71.08 g of off-white solids were collected (after        solvent evaporation) and labeled ‘Fraction 2’.    -   7. The hexanes solvent was removed from all samples via        evaporation and then the samples were allowed to degas at room        temperature and pressure for at least two days before being        characterized using the test methods disclosed herein.

The data for the fraction 1 sample collected at 200 psig (1.38 MPa) aresummarized in Table 1.

The solids isolated in fraction 1 of this example were slightlyoff-white in color. When these fraction 1 solids were compression moldedinto square test specimens, the specimens were nearly colorless but wereslightly cloudy in appearance. A photograph of the square test specimenis shown in FIG. 4 as Example 4. As shown in FIG. 4, the specimen had animproved color and opacity relative to example 1, however, the specimenalso had a cloudy appearance when compared to virgin PP. The L*a*b*values showed the fraction 1 square test specimens were essentiallycolorless and showed an improvement in color relative to the square testspecimens of example 1 (i.e. as-received post-consumer derivedpolypropylene). The L* values for the square test specimens fromfraction 1 of example 4 averaged 82.18 which were much improved whencompared to the L* values for the square test specimens of example 1,which averaged 39.76. The opacity for the square test specimens fromfraction 1 of example 4, which averaged 22.18% opaque, were alsoimproved when compared to the opacity values for the square testspecimens of example 1, which averaged about 100% opaque. However, theopacity values for the square test specimens from fraction 1 of example4 were not as improved as the opacity values for the square testspecimens from fraction 2 of examples 2 and 3.

The concentration of heavy metal contamination for the samples fromfraction 1 of example 4 were also much improved when compared to thesamples of example 1. For example, the concentration of sodium in thesamples from fraction 1 of example 4 averaged 2,790 ppb while theconcentration of sodium in the samples of example 1 averaged 136,000 ppb(a reduction of about 97%). The concentrations of aluminum, calcium,titanium, chromium, iron, nickel, copper, zinc, cadmium, and lead wereall reduced by greater than 96% for the samples from fraction 1 ofexample 4 relative to the samples of example 1.

The samples from fraction 1 of example 4 had ash content values thataveraged to about 0.2812 wt %, which was significantly lower than theash content values for the samples of example 1, which averaged to about1.2117 wt %.

The samples from fraction 1 of example 4 were found to have an odorintensity of 2.25 on a 5 point scale (5 being most intense), which wasimproved when compared to the odor intensity of the samples of example1, which had an odor intensity of 3.75. Though lower in intensity, thesamples from fraction 1 of example 4 had odor described as being“minty”, “sour”, “plastic”, and “burnt.”

The samples from fraction 1 of example 4 had average polyethylenecontent values of about 1.9 wt %, which was improved when compared tothe polyethylene content of the samples of example 1, which averaged toabout 5.5 wt %.

Example 5

The sample of post-consumer derived recycled polypropylene mixed colorflake described in Example 1 was processed using the experimentalapparatus shown in FIG. 3 and the following procedure:

-   -   1. 233 g of the mixed color flake was loaded into a 1.1 L        extraction column pressure vessel with an internal diameter (ID)        of 1.75″ (44.45 mm) and a length of 28″ (71.12 cm) that was        heated to an external skin temperature of 175° C.    -   2. Liquid n-butane solvent was pressurized to about 2,050 psig        (14.13 MPa) using a positive displacement pump and pre-heated to        a temperature of about 110° C. using two heat exchangers before        it was introduced to the bottom of the extraction column.    -   3. The fluid stream leaving the top of the extraction column was        introduced into the top of a second 0.5 L pressure vessel with        an ID of 2″ (50.8 mm) and a length of about 8.5″ (21.59 cm) that        was heated to an external skin temperature of 175° C. The second        pressure vessel contained 180 mL of silica gel (Silicycle Ultra        Pure Silica Gels, SiliaFlash GE60, Parc-Technologies, USA).    -   4. The fluid stream leaving the bottom of the second pressure        vessel was depressurized across an expansion valve into a        side-arm Erlenmeyer flask. After depressurizing the fluid stream        into the Erlenmeyer flask, the solvent vapor was vented through        the side-arm port and any liquids/solids collected in the flask.        The n-butane solvent was eluted through the system at 2,050 psig        (14.13 MPa) until no further material was observed accumulating        in the flask. 12.87 g of white solids were collected and labeled        ‘Fraction 1’.    -   5. The Erlenmeyer flask was replaced with an empty, clean flask        and the system pressure was then increased to 2,500 psig (17.24        MPa).    -   6. The system pressure was maintained at 2,500 psig (17.24 MPa)        until no further solid material was observed eluting from the        system. 162.43 g of white solids were collected and labeled        ‘Fraction 2’.    -   7. The sample collected at 2,500 psig (17.24 MPa) was then        allowed to degas at room temperature and pressure for at least        two days before it was characterized using the test methods        disclosed herein.

The data for the fraction 2 sample collected at 2,500 psig (17.24 MPa)are summarized in Table 2.

The solids isolated from fraction 2 in this example were white toslightly off-white in color. When these fraction 2 solids werecompression molded into square test specimens, the specimens were nearlycolorless but were slightly cloudy in appearance. A photograph of thesquare test specimen is shown in FIG. 4 as Example 5. As shown in FIG.4, the specimen had an improved appearance relative to example 1, butwas slightly cloudy when compared to virgin PP. The L*a*b* values showedthe square test specimens were essentially colorless and showed adramatic improvement in color relative to the square test specimens ofexample 1 (i.e. as-received post-consumer derived polypropylene). The L*values for the square test specimens from fraction 2 of example 5averaged 82.00 which were much improved when compared to the L* valuesfor the square test specimens of example 1, which averaged 39.76. Theopacity for the square test specimens from fraction 2 of example 5,which averaged about 18.63% opaque, were also improved when compared tothe opacity values for the square test specimens of example 1, whichaveraged about 100% opaque. However, the opacity values for the squaretest specimens from fraction 2 of example 5 were not as improved as theopacity values for the square test specimens from fraction 2 of examples2 and 3. Though not wishing to be bound by any theory, the applicantsbelieve that the improved, but still cloudy appearance was due to thesmaller charge of silica gel (i.e. shorter bed length) which allowedmore contaminants to remain in the polymer collected.

The concentration of heavy metal contamination in the samples fromfraction 2 of example 5 were also much improved when compared to thesamples of example 1. For example, the concentration of sodium in thesamples from fraction 2 of example 5 averaged 2,960 ppb while theconcentration of sodium in the samples of example 1 averaged 136,000 ppb(a reduction of about 98%). The concentrations of iron in the samplesfrom fraction 2 of example 5 were below the limit of quantitation whilethe concentrations of iron in the samples of example 1 averaged 108,000.The concentrations of aluminum, calcium, titanium, chromium, nickel,copper, zinc, cadmium, and lead were all reduced by greater than 97% forthe samples from fraction 2 of example 5 relative to the samples ofexample 1.

The samples from fraction 2 of example 5 had ash content values thataveraged to about 0.5723 wt %, which was lower than the ash contentvalues for the samples of example 1, which averaged to about 1.2117 wt%.

The samples from fraction 2 of example 5 were found to have an odorintensity of 4 on a 5 point scale (5 being most intense), which wasslightly higher when compared to the odor intensity of the samples ofexample 1, which had an odor intensity of 3.75. The samples fromfraction 2 of example 5 had an odor described as “dirty”, “oily”, and“minty” Though not wishing to be bound by any theory, the applicantsbelieve that the higher odor intensity of the samples of example 5resulted from the absorption of odorant molecules into silica gel duringthe first extraction step (i.e. collection of Fraction 1). Due to thelower amount of silica gel (and thus shorter bed height) used in example5, the absorbed odorant molecules likely eluted with the solidscollected as Fraction 2.

The samples from fraction 2 of example 5 had polyethylene content valuesthat averaged to about 1.7 wt %, which were improved when compared tothe polyethylene content of the samples of example 1, which averaged toabout 5.5 wt %.

Example 6

The samples of example 6 were produced by combining the fraction 1 whitesolids produced at 1,000 psig (6.89 MPa) in example 3 with the fraction2 white solids produced at 1,500 psig (10.34 MPa) in example 3. Thecombined fraction 1 and fraction 2 sample was produced to demonstratethe performance of a method to purify polypropylene without the step ofextracting any extractable contamination. The data for the combinedfractions 1 and 2 of example 3 are summarized in Table 2.

When the solids of this example were compression molded into square testspecimens, the specimens had an appearance similar to the square testspecimens from fraction 2 of example 3. A photograph of the square testspecimen is shown in FIG. 4 as Example 6. As shown in FIG. 4, thespecimen was clear and comparable in color and translucency to virginpolypropylene. The L*a*b* values showed the square test specimens wereessentially colorless and showed a dramatic improvement in colorrelative to the square test specimens of example 1 (i.e. as-receivedpost-consumer derived polypropylene). The L* values for the square testspecimens of example 6 averaged 84.51 which were much improved whencompared to the L* values for the square test specimens of example 1,which averaged 39.76. The opacity for the square test specimens ofexample 6, which averaged 9.14% opaque (i.e. nearly 91% translucent),were also much improved when compared to the opacity values for thesquare test specimens of comparative example 1, which averaged about100% opaque. The L*a*b* values and opacities of the square testspecimens of example 6 were also similar to the L*a*b* values andopacities of the square test specimens from fraction 2 of example 3.

Similar to fraction 2 of example 3, the concentration of heavy metalcontamination in the samples of example 6 were also much improved whencompared to the samples of example 1. For example, the concentration ofsodium in the samples of example 6 averaged 19,700 ppb while theconcentration of sodium in the samples of example 1 averaged 136,000 ppb(a reduction of about 86%). The concentrations of aluminum, calcium,titanium, chromium, iron, nickel, copper, zinc, cadmium, and lead wereall reduced by greater than 82% for the samples of example 6 relative tothe samples of example 1.

The samples of example 6 had average ash content values of about 0.4951wt %, which was lower than the average ash content values for thesamples of example 1, of about 1.2117 wt %. When compared to the ashcontent values for the samples from fraction 2 of example 3, the ashcontent values for the samples of example 6 were slightly higher.

The samples of example 6 were found to have an odor intensity of 3.75 ona 5 point scale (5 being most intense), which was similar to the odorintensity of the samples of example 1, which had an odor intensity of3.75 as well. The samples of example 6 had odor described as “chlorine”,“plastic”, “oily”, and “greasy.” When compared to the samples fromfraction 2 of example 3, the samples of example 6 had a more intenseodor.

Similar to fraction 2 of example 3, any polyethylene content in thesamples of example 6 was below the limit of quantitation, which was muchimproved when compared to the polyethylene content of the samples ofexample 1, which averaged to about 5.5 wt %.

Example 7

The purpose of this example was to demonstrate the inferior performanceof a method to purify polypropylene without the step of contacting apolymer solution with solid media. The sample of post-consumer derivedrecycled polypropylene mixed color flake described in Example 1 wasprocessed using the experimental apparatus shown in FIG. 3 and thefollowing procedure:

-   -   1. 231 g of the mixed color flake was loaded into a 1.1 L        extraction column pressure vessel with an internal diameter (ID)        of 1.75″ (44.45 mm) and a length of 28″ (71.12 cm) that was        heated to an external skin temperature of 175° C.    -   2. Liquid n-butane solvent was pressurized to about 2,000 psig        (13.79 MPa) using a positive displacement pump and pre-heated to        a temperature of about 110° C. using two heat exchangers before        it was introduced to the bottom of the extraction column.    -   3. The fluid stream leaving the top of the extraction column was        introduced into the top of a second 0.5 L pressure vessel with        an ID of 2″ (50.8 mm) and a length of about 8.5″ (21.59 cm) that        was heated to an external skin temperature of 175° C. The second        pressure vessel did not contain any solid media in this example.    -   4. The fluid stream leaving the bottom of the second pressure        vessel was depressurized across an expansion valve into a        side-arm Erlenmeyer flask. After depressurizing the fluid stream        into the Erlenmeyer flask, the solvent vapor was vented through        the side-arm port and any liquids/solids were collected in the        flask. The n-butane solvent was eluted through the system at        2,000 psig (13.79 MPa) until no further material was observed        accumulating in the flask. 20.82 g of tan solids were collected        and labeled ‘Fraction 1’.    -   5. The Erlenmeyer flask was replaced with an empty, clean flask        and the system pressure was then increased to 2,500 psig (17.24        MPa).    -   6. The system pressure was maintained at 2,500 psig (17.24 MPa)        until no further solid material was observed eluting from the        system. 173.39 g of grayish white solids were collected and        labeled ‘Fraction 2’.    -   7. The fraction 2 sample collected at 2,500 psig (17.24 MPa) was        then allowed to degas at room temperature and pressure for at        least two days before it was characterized using the test        methods disclosed herein.

The data for the fraction 2 sample collected at 2,500 psig (17.24 MPa)are summarized in Table 2.

The solids isolated in fraction 2 in this example were gray to off-whitein color. When these fraction 2 solids were compression molded intosquare test specimens, the specimens were tan/light gray in appearance.A photograph of the square test specimen is shown in FIG. 4 as Example7. As shown in FIG. 4, the specimen was slightly improved relative toexample 1. Even without the solid media contact step, the L*a*b* valuesshow that the square test specimens from fraction 2 of example 7 wereslightly improved in color relative to the samples of example 1 (i.e.as-received post-consumer derived polypropylene). The L* values for thesquare test specimens from fraction 2 of example 7 averaged 50.51 whichwere slightly improved when compared to the L* values for the squaretest specimens of example 1, which averaged 39.76. The opacities for thesquare test specimens from fraction 2 of example 7, which averaged87.20% opaque, were also slightly improved when compared to the opacityvalues for the square test specimens of example 1, which averaged about100% opaque. Though not wishing to be bound by any theory, the slightimprovement in the color values and opacities of the square testspecimens of example 7 may be due to the extraction of polymer from thecolorants and other materials responsible for appearance. Further, theapplicants believe that the colorants and other materials may be leftbehind as a residuum after the polymer is extracted.

The concentration of heavy metal contamination in the samples fromfraction 2 of example 7 were improved when compared to the samples ofexample 1. For example, the concentration of sodium in the samples fromfraction 2 of example 7 averaged 33,300 ppb while the concentration ofsodium in the samples of example 1 averaged 136,000 ppb (a reduction ofabout 76%). The concentrations of aluminum, calcium, titanium, chromium,iron, nickel, copper, zinc, cadmium, and lead were all reduced bygreater than 69% for the samples from fraction 2 of example 7 relativeto the samples of example 1. Though not wishing to be bound by anytheory, the applicants believe that the reduction in heavy metalscontamination results from the extraction of the polymer away from thecontamination, which is left behind as a residuum after the polymer isextracted.

The samples from fraction 2 of example 7 had ash content values thataveraged to about 0.3154 wt %, which was lower than the ash contentvalues for the samples of example 1, which averaged to about 1.2117 wt%.

The samples from fraction 2 of example 7 were found to have an odorintensity of 1 on a 5 point scale (5 being most intense), which was muchimproved when compared to the odor intensity of the samples of example1, which had an odor intensity of 3.75. The samples from fraction 2 ofexample 7 had odor described as being like “plastic” or “petroleum.”

The samples from fraction 2 of example 7 had polyethylene content valuesthat averaged to about 1.2 wt %, which was improved when compared to thepolyethylene content of the samples of example 1, which averaged toabout 5.5 wt %.

Example 8

The sample of post-consumer derived recycled polypropylene mixed colorflake described in Example 1 was purified using a procedure based on theprocedure described in EP0849312 A1.

20.00 g of post-consumer derived recycled polypropylene mixed colorflake was combined with 400.04 g of white spirits (Sigma-Aldrich, USA)in a 1 L round-bottomed flask. The mixture was held at room temperaturefor 22 hours with occasional stirring. The white spirits was thendecanted from the polymer. 402.60 g of fresh white spirits was added tothe flask containing the polymer. The mixture was then heated and heldat 140° C. for 90 min under reflux. The resulting hot solution wasvacuum filtered through a 70 mm ID Buchner funnel with a layer of glasswool as the filtration medium. About 300 mL of filtrate was collectedand allowed to cool to room temperature. The resulting gray precipitatewas isolated via vacuum filtration through a 70 mm ID Buckner funnelwith shark skin filter paper. The gray precipitate was combined with2.01 g of Fuller's earth (Sigma-Aldrich, USA) and 195.21 g of freshwhite spirits in a 1 L round-bottomed flask and then heated and held at140° C. for 30 min under reflux. The resulting hot solution was vacuumfiltered through a 5.5 cm ID Buchner funnel with shark skin filterpaper. The filtrate was allowed to cool to room temperature. Theresulting light gray precipitate was isolated via vacuum filtrationthrough a 5.5 cm ID Buchner funnel with shark skin filter paper. Theisolated precipitate was dried in a vacuum oven at 25° C. for about 18hours. About 4.82 g of dried precipitate was isolated. The isolatedprecipitate was then extracted with acetone for 30 min using a Soxhletextraction apparatus equipped with a cellulose extraction thimble. Theextracted material was dried in a vacuum oven at 25° C. for about 19hours. 3.4654 g of material was recovered. The sample was characterizedusing the test methods disclosed herein and the resulting data aresummarized in Table 2.

The solids isolated in this example were light gray to off-white incolor. When these solids were compression molded into square testspecimens, the specimens had a smoky, faint-gray appearance. Aphotograph of the square test specimen is shown in FIG. 4 as Example 8.As shown in FIG. 4, the specimen was improved but remained dark in colorwas not as clear and translucent as virgin PP. The L*a*b* value showedthe sample color was improved relative to the samples of example 1 (i.e.as-received post-consumer derived polypropylene). The L* value for thesample of example 8 was 63.15 which was improved when compared to the L*values for the sample of example 1, which averaged 39.76. However, theL* value for the sample of example 8 demonstrates that the methoddescribed in EP0849312 A1 does not produce a sample that is as brightand colorless as samples from some of the embodiments of the presentinvention. The opacity for the sample of example 8 was 24.96% opaque,which was improved when compared to the opacity values for the samplesof example 1, which averaged about 100% opaque. The opacity value alsoshows that the sample of example 8 was not as translucent as some of theembodiments of the present invention.

The concentration of heavy metal contamination in the sample of example8 was improved when compared to the samples of example 1. For example,the concentration of sodium in the sample of example 8 was 5,120 ppbwhile the concentration of sodium in the samples of example 1 averaged136,000 ppb (a reduction of about 96%). The concentrations of aluminum,calcium, titanium, chromium, iron, nickel, copper, zinc, cadmium, andlead were all reduced by greater than 43% for the sample of example 8relative to the samples of example 1.

The sample of example 8 had an ash content of about 0.3294 wt %, whichwas lower than the ash content values for the samples of example 1,which averaged to about 1.2117 wt %.

The samples of example 8 had an odor intensity of 5 on a 5 point scale(5 being most intense), which was much stronger when compared to theodor intensity of the samples of example 1, which had an odor intensityof 3.75. The samples of example 3 had odor described as being like“gasoline.” The strong odor of this sample was due to the residual whitesprits solvent used.

The sample of example 8 had average polyethylene content values of about5.5 wt %, which was the same as the average polyethylene content of thesamples of example 1 of about 5.5. wt %.

Virgin Polypropylene Comparative Samples

Pro-fax 6331 polypropylene (LyondellBasell Industries Holdings, B.V.)was used for all “Virgin PP” comparative samples. The pellets of virginPP were processed into square test specimens according the methoddescribed herein. The L*a*b* values for the specimens made from virginPP averaged to 85.13±0.18, −0.71±0.01, and 2.27±0.02, respectively Thesquare test specimens had an average opacity of 7.56±0.21% opaque. Thepellets of virgin PP had an odor intensity of 0.5 on a 5 point scale (5being the most intense) and had odor described as being like “plastic.”

Example 9

A sample of post-consumer derived recycled high-density polyethylene wassourced from a supplier of recycled resins. The post-consumer recycledpolyethylene was classified as “natural color” and originated from theUnited Kingdom. The as-received pellets were characterized using thetest methods disclosed herein and the resulting data are summarized inTable 3. The purpose of this example is to show the properties of arepresentative post-consumer derived recycled polyethylene resin beforebeing purified according to an embodiment of the present invention.

The pellets and corresponding square test specimens were off-white incolor as indicated in the L*a*b* values of the square test specimens.The opacity of the sample of example 9 was about 81.61% opaque. Aphotograph of the square test specimen is shown in FIG. 6 as Example 9.

This example serves as a representative baseline for heavy metalcontamination found in post-consumer derived recycled polyethylene. Whencompared to the other example, the heavy metal contamination was foundto be greater in the as-received post-consumer derived recycledpolyethylene.

The samples of example 9 had ash content values that averaged to about0.8513 wt %, which also serves as a baseline for the amount ofnon-combustible substances that may be present in post-consumer derivedrecycled polyethylene.

This example also serves as a representative baseline for odor compoundcontamination found in post-consumer derived recycled polyethylene. Thesamples of example 9 were found to have an odor intensity of 2.5 on a 5point scale (5 being most intense).

Example 10

The sample of post-consumer derived recycled polyethylene described inexample 9 was processed using the experimental apparatus shown in FIG. 3and the following procedure:

-   -   1. 237 g of the polyethylene pellets were loaded into a 1.1 L        extraction column pressure vessel with an internal diameter (ID)        of 1.75″ (44.45 mm) and a length of 28″ (71.12 cm) that was        heated to an external skin temperature of 175° C.    -   2. Liquid n-butane solvent was pressurized to about 4,500 psig        (31.03 MPa) using a positive displacement pump and pre-heated to        a temperature of about 110° C. using two heat exchangers before        it was introduced to the bottom of the extraction column.    -   3. The fluid stream leaving the top of the extraction column was        introduced into the top of a second 0.5 L pressure vessel with        an ID of 2″ (50.8 mm) and a length of about 8.5″ (21.59 cm) that        was heated to an external skin temperature of 175° C. The second        pressure vessel contained 150 mL of silica gel (Silicycle Ultra        Pure Silica Gels, SiliaFlash GE60, Parc-Technologies, USA) that        was pre-mixed in a beaker with 150 mL of aluminum oxide        (Activated Alumina, Selexsorb CDX, 7×14, BASF, USA).    -   4. The fluid stream leaving the bottom of the second pressure        vessel was depressurized across an expansion valve into a        side-arm Erlenmeyer flask. After depressurizing the fluid stream        into the Erlenmeyer flask, the solvent vapor was vented through        the side-arm port and any liquids/solids were collected in the        flask. The n-butane solvent was eluted through the system at        4,500 psig (31.03 MPa) until no further material was observed        accumulating in the flask. 3.93 g of white solids were collected        and labeled as ‘Fraction 1’.    -   5. The Erlenmeyer flask was replaced with an empty, clean flask        and the system pressure was then increased to 5,000 psig (34.47        MPa).    -   6. The system pressure was maintained at 5,000 psig (34.47 MPa)        until no further solid material was observed eluting from the        system. 33.19 g of white solids were collected and labeled as        ‘Fraction 2’.

The data for the fraction 2 samples collected at 5,000 psig (34.47 MPa)are summarized in Table 3.

The fraction 2 solids isolated in this example were white to off-whitein color. When the fraction 2 solids were compression molded into squaretest specimens, the specimens were off-white. A photograph of the squaretest specimen is shown in FIG. 3 as Example 10. As shown in FIG. 6, thespecimen was more translucent than the untreated PE and was similar inopacity to virgin polyethylene. The L*a*b* values also show that thesquare test specimens from fraction 2 of example 10 showed animprovement in color relative to the samples of example 1 (i.e.as-received post-consumer derived polyethylene). The L* values for thesquare test specimens from fraction 2 of example 10 averaged 85.20 whichwere improved when compared to the L* values for the sample of example9, which averaged 80.28. The opacity for the square test specimens fromfraction 2 of example 10, which averaged 53.20% opaque, were alsoimproved when compared to the opacity values for the samples of example9, which averaged about 81.61% opaque.

The concentration of heavy metal contamination in the samples fromfraction 2 of example 10 were also improved when compared to the samplesof example 9. For example, the concentration of sodium in the samplesfrom fraction 2 of example 10 averaged 6,620 ppb while the concentrationof sodium in the samples of example 9 averaged 19,800 ppb (a reductionof about 67%). The concentrations of all of the other elements measuredwere all reduced by greater than 66% for the samples from fraction 2 ofexample 10 relative to the samples of example 9.

The samples from fraction 2 of example 10 had ash content values thataveraged to about 0.5032 wt %, which were lower than the ash contentvalues for the samples of example 9, which averaged to about 0.8513 wt%.

The samples from fraction 2 of example 10 were found to have an odorintensity of 0.5 on a 5 point scale (5 being most intense), which wasimproved when compared to the odor intensity of the samples of example9, which had an odor intensity of 2.5.

FIG. 7 is a bar chart of the opacity and odor intensity of the purifiedrecycled polyethylene of example 10 compared to the untreated recycledpolyethylene (example 9), and a virgin polyethylene comparative sample.As shown in FIG. 7, the purified recycled polyethylene of example 10 hadan improved opacity and odor intensity.

TABLE 3 Color, contamination, and odor removal of Examples 9 and 10Example 9 Example 10 Fraction N/A Fraction 2 Solid Media N/A 150 mL ofsilica gel mixed with 150 mL of aluminum oxide Color L* 80.28 85.20 (n= 1) (n = 1) Color a* −3.85 −2.37 (n = 1) (n = 1) Color b*  5.47  4.62(n = 1) (n = 1) Opacity (Y) 81.61 53.20 Na (ppb) 19,800 ± 6,620 ± LOQ =100 ppb 2,380 1,320 (n = 5) (n = 5) Al (ppb) 37,600 ± 7,100 ± LOQ = 1000ppb 3,010 142 (n = 5) (n = 5) Ca (ppb) 126,000 ± 13,600 ± LOQ = 1000 ppb0 952 (n = 5) (n = 5) Ti (ppb) 1,040,000 ± 171,000 ± LOQ = 100 ppb41,600 5,130 (n = 5) (n = 5) Cr (ppb) 3,070 ± 1,030 ± LOQ = 10 ppb 1,600144 (n = 5) (n = 5) Fe (ppb) 18,400 ± 4,040 ± LOQ = 1000 ppb 552 1,490(n = 5) (n = 5) Ni (ppb) 28.9 ± <LOQ LOQ = 10 ppb 11.9 (n = 5) Cu (ppb)391 ± 86.5 ± LOQ = 10 ppb 31.3 4.33 (n = 5) (n = 5) Zn (ppb) 14,800 ±2,970 ± LOQ = 10 ppb 1,330 238 (n = 5) (n = 5) Cd (ppb) <LOQ <LOQ LOQ =10 ppb Pb (ppb) 197 ± 29.6 40.3 ± 1.21 LOQ = 10 ppb (n = 5) (n = 5) AshContent 0.8513 + 0.5032 ± (% res 0.0898 0.1356 from TGA) (n = 2) (n = 2)Odor Intensity 2.5 0.5 (0-5)Virgin Polyethylene Comparative Samples

Dow 6850A polyethylene (The Dow Chemical Company, USA) was used for all“Virgin PE” comparative samples. The pellets of virgin PE were processedinto square test specimens according the methods described herein. TheL*a*b* values for the specimens made from virgin PE averaged to84.51±0.97, −1.03±0.04, and −0.63±0.12, respectively The square testspecimens had an average opacity of 34.68±0.69% opaque. The pellets ofvirgin PE had an odor intensity of 0.5 on a 5 point scale (5 being themost intense) and had odor described as being like “plastic.”

Every document cited herein, including any cross reference or relatedpatent or patent application, is hereby incorporated herein by referencein its entirety unless expressly excluded or otherwise limited. Thecitation of any document is not an admission that it is prior art withrespect to any invention disclosed or claimed herein or that it alone,or in any combination with any other reference or references, teaches,suggest or discloses any such invention. Further, to the extent that anymeaning or definition of a term in this document conflicts with anymeaning or definition of the same term in a document incorporated byreference, the meaning or definition assigned to that term in thisdocument shall govern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modification can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodification that are within the scope of the present invention.

What is claimed is:
 1. A method for purifying a reclaimed polymercomprising: a. Obtaining the reclaimed polymer wherein said reclaimedpolymer is selected from the group consisting of post-consumer usepolymers, post-industrial use polymers, and combinations thereof; b.Contacting the reclaimed polymer at a temperature from about 80° C. toabout 220° C. and at a pressure from about 150 psig (1.03 MPa) to about15,000 psig (103.42 MPa) with a first fluid solvent having a standardboiling point less than about 70° C., to produce an extracted reclaimedpolymer; c. Dissolving the extracted reclaimed polymer in a solventselected from the group consisting of the first fluid solvent, a secondfluid solvent, and mixtures thereof, at a temperature from about 90° C.to about 220° C. and a pressure from about 350 psig (2.41 MPa) to about20,000 psig (137.90 MPa) to produce a polymer solution; d. Purifyingsaid polymer solution at a temperature from about 90° C. to about 220°C. and at a pressure from about 350 psig (2.41 MPa) to about 20,000 psig(137.90 MPa) by contacting said polymer solution with solid media toproduce a purer polymer solution; and e. Separating a purer polymer fromsaid purer polymer solution; wherein said second fluid solvent has thesame chemical composition or a different chemical composition as thefirst fluid solvent.
 2. The method of claim 1, wherein the purer polymeris separated from said purer polymer solution at a temperature fromabout 0° C. to about 220° C. and a pressure from about 0 psig (0 MPa) to2,000 psig (13.79 MPa).
 3. The method of claim 1, wherein the reclaimedpolymer is post-consumer recycle derived polymer.
 4. The method of claim1, wherein said reclaimed polymer is polystyrene.
 5. The method of claim1, wherein said reclaimed polymer is poly(dimethylsiloxane).
 6. Themethod of claim 1, wherein said reclaimed polymer is a polypropylenehomopolymer or a primarily polypropylene copolymer.
 7. The method ofclaim 1, wherein said polymer is a polyethylene homopolymer or aprimarily polyethylene copolymer.
 8. The method of claim 1, wherein saidfluid solvent has a standard boiling point less than about 0° C. andgreater than about −45° C. and a standard enthalpy change ofvaporization of less than about +25 kJ/mol.
 9. The method of claim 1,wherein said fluid solvent is selected from the group consisting ofolefinic hydrocarbons, aliphatic hydrocarbons, and mixtures thereof. 10.The method of claim 9, wherein said aliphatic hydrocarbon is selectedfrom the group consisting of C₁-C₆ aliphatic hydrocarbons and mixturesthereof.
 11. The method of claim 9, wherein said aliphatic hydrocarbonsand mixtures thereof is comprised of primarily C₄ aliphatichydrocarbons.
 12. The method of claim 9, wherein said fluid solventconsists essentially of C₄ liquefied petroleum gas.
 13. The method ofclaim 10, wherein said fluid solvent is n-butane, butane isomers, ormixtures thereof.
 14. The method of claim 1, wherein said temperature insteps b, c, and d is from about 110° C. to about 170° C.
 15. The methodof claim 1, wherein said pressure in step b is from about 1,100 psig(7.58 MPa) to about 5,500 psig (37.92 MPa).
 16. The method of claim 1,wherein said pressure in step b is less than about 1,100 psig (7.58MPa).
 17. The method of claim 1, wherein said pressure in step c isgreater than about 1,100 psig (7.58 MPa).
 18. The method of claim 1,wherein said pressure in step c is greater than about 5,500 psig (37.92MPa).
 19. The method of claim 1, wherein said solid media is selectedfrom the group consisting of inorganic substances, carbon-basedsubstances, and mixtures thereof.
 20. The method of claim 18, whereinsaid inorganic substances are selected from the group consisting ofoxides of silicon, oxides of aluminum, oxides of iron, aluminumsilicates, amorphous volcanic glasses, and mixtures thereof.
 21. Themethod of claim 18, wherein said inorganic substances are selected fromthe group consisting of silica, silica gel, diatomite, sand, quartz,alumina, perlite, fuller's earth, bentonite, and mixtures thereof. 22.The method of claim 18, wherein said inorganic substances is reclaimedglass.
 23. The method of claim 18, wherein said carbon-based substancesare selected from the group consisting of anthracite coal, carbon black,coke, activated carbon, cellulose, and mixtures thereof.
 24. The methodof claim 1, wherein said contacting of the polymer solution with saidsolid media is done in a packed bed of said solid media.
 25. The methodof claim 23, where said packed bed is greater than 20 cm in length.